control guide management of noise at work
TRANSCRIPT
CONTROL GUIDE
MANAGEMENT OFNOISE AT WORK
OCCUPATIONAL SAFETY & H E A LT H S E R V I C E
L A B O U R D E P A R T M E N T O F
T E T A R I M A H I
ii
Acknowledgment
The Occupational Safety & Health Service wishes tothank the National Occupational Health and SafetyCommission, Sydney (Worksafe Australia) for theirpermission to use the material in this guide. Thematerial is based on the National OccupationalHealth and Safety Commission’s publication NoiseManagement at Work: Control Guide (ISBN 0644-12866-6).
Published by the Occupational Safety and HealthService,Department of Labour,Wellington,New Zealand.
First Edition: November 1996
ISBN 0477-03569-8
Price $50 (incl. GST).
iii
CONTENTS
PREFACE
OVERVIEW
CORE CONTENTS
MODULE SUMMARIES
STRUCTURE OF THE GUIDE
USING THE GUIDE
NOISE MANAGEMENT FLOW CHART
CORE STEPS 1-5
MODULES 1-12
iv
PREFACE
The Occupational Safety & Health Service (OSH) ControlGuide: Management of Noise at Work has been prepared inresponse to a problem which resulted in over 9,000workers’ compensation claims to ACC in the 1991-92 yearfor industrial deafness and cost the nation $38 million incompensation payments alone.
Noise-induced hearing loss (NIHL) is one of the priorityareas for action of the Occupational Safety & HealthService. The Service’s national strategy for the preventionof occupational noise-induced hearing loss, which sets aframework for national action on this issue, has beenendorsed by employer and employee organisations.
Elements of the national strategy include the promotion ofpreventive measures; development of materials to assistworkplace prevention, training and education; research;and the development of legislation, standards and anapproved code of practice.
The legislative framework for noise exposure prevention,which sets noise exposure limits and responsibilities foremployers and employees, is in place. The OccupationalSafety & Health Service has developed regulations onoccupational noise and issued an approved code of practicefor the management of noise and the protection of hearingat work.
Legislation on its own, however, is not enough. It isimportant to understand that effective prevention requiresthat managers, workers and the general public have abetter understanding of the potential for noise-inducedhearing loss and access to information about how tocontrol noise.
v
OVERVIEW
The Control Guide: Management of Noise at Workprovides step by step guidance to assist organisations toeffectively manage workplace noise and prevent noise-induced hearing loss.
The best way to control noise is to purchase quieterequipment in future, and to apply noise controlmeasures to existing noisy equipment.
For some workplaces in some industries, achieving safenoise levels may require the application of noisemanagement policies, planning and budgeting over anumber of years.
While these control measures are being formulated andimplemented, employees need to be protected from theeffects of unsafe levels of noise through personalhearing protection programmes. To be effective, suchprogrammes must be carefully managed. This guidetherefore provides comprehensive information to assistorganisations to conduct an effective personalprogramme as an interim measure for those employeesat risk.
To summarise, this guide provides the informationneeded by management to implement a comprehensiveprogramme and strategy for managing noise. Theessential ingredient from management is commitmentto action, shown through personal involvement and theallocation of adequate resources.
vi
CORE MODULE CONTENTS
Structure of the Control Guide
Using the Control Guide
Noise Management Flow Chart
STEP 1 Establish a Basis for ActionIntroductionWhat does the law say?What harm does noise do?What if we don’t do anything?Haven’t we done enough already?What does it cost to deal with noise?Conclusion
STEP 2 Assess Your Present PositionNominate a noise managerEstablish consultative processConduct a walk-through auditEvaluate present measuresInterim noise managementConduct a noise survey
STEP 3 Set Goals and PoliciesIntroductionPolicy issuesResponsibilities and obligations
STEP 4 Establish a Noise Management StrategyIntroductionBuy quiet programmeNoise control planPersonal protection programme
STEP 5 Monitor and EvaluateIntroductionMonitoring programme implementationEvaluationA note on audiometryMonitoring checklist
APPENDIX 1 Glossary of Technical Terms
APPENDIX 2 Measures of Noise Exposure
APPENDIX 3 Directory of Products and Services
vii
MODULE SUMMARIES
Case StudiesCase Study 1: Waratah Wire ProductsCase Study 2: Johnson and Johnson
A Walk-Through Assessment of your WorkplaceSetting it UpAssessment Procedure
Reducing Noise through “In-House”Maintenance, Modification and Upgradingof PlantWhat you will needOverview of Maintenance and ModificationPractical DiagnosisDiagnostic TestsMaintenance or Modification?Upgrading the PlantMinimising Maintenance NoiseConclusionReferenced DocumentsAppendix
Getting the Best from Consultants andContractorsConsultant or Contractor?Using a Consultant or ContractorSummary
Understanding and Using Noise Survey ReportsPurpose of a Noise SurveyWhat you need to use a SurveyDefine Scope of SurveyIdentify Exposed EmployeesDescribe Plant Operating ConditionsAssess Risk to EmployeesIdentify Areas of Highest ExposureSelect Hearing ProtectorsProvide InformationDefine Statutory ObligationsSummary
Costs of Noise and Benefits of Noise ControlOverviewIntroductionCosts of Noise to OrganisationsCosts of Noise to Exposed PersonnelBenefits of Noise Control for the OrganisationBenefits of Noise Control for Exposed PersonnelReferenced Documents
Developing a Noise Policy for your WorkplaceWhat is a Noise Policy?Purposes of a Noise PolicyBenefits of a Noise PolicyFactors to take into AccountSpecific Issues that may be dealt with
MODULE 1CASE STUDIES
MODULE 2
WALK THROUGHAUDIT
MODULE 3
IN-HOUSECONTROL
MODULE 3
CONSULTANTS
MODULE 5
USING SURVEYS
MODULE 6
COSTS/BENEFITS
MODULE 7
NOISE POLICY
viii
Developing the Organisation’s Noise PolicyUsing the PolicyFurther Reading
Buy Quiet Purchasing Policy and ProceduresIntroductionBasic Buy Quiet RulesPurchasing Procedure OverviewPolicy and Procedural IssuesFurther Reading
Evaluating Noise Control OptionsIdentifying Noise Control OptionsEstimating the Effectiveness of OptionsSelecting the Most Effective Treatment OptionCosting the OptionsExample: Stamping Numbers on Steel GasCylindersImplementing the Chosen SolutionBasic Noise ControlFurther Reading
Fact SheetsFACT SHEET 1: Effects of Noise and Value of
Good HearingFACT SHEET 2: Questions and Answers on
Noise and Noise ControlFACT SHEET 3: Ways of avoiding Hearing
DamageFACT SHEET 4: Hearing Protectors
Training and InformationIntroductionSenior ManagersProduction Managers, Engineers and TechniciansEmployees and Supervisors
SESSION 1: Noise, a Major IssueSESSION 2: Noise, an Issue in this OrganisationSESSION 3: Identifying and Solving Noise
ProblemsSESSION 4: The Effective Use of Personal
Hearing Protection Evaluation
Setting up an Effective Personal ProtectionProgrammeOverviewSelecting Hearing Protectors with Adequate NoiseReductionSelect the Right Protectors for each PersonCompatibility with the WorkAcceptability to the WearerMonitoring the Use of Hearing ProtectorsHearing Protector Maintenance ChecklistsProblemsFurther Reading
MODULE 7
NOISE POLICY
MODULE 8
BUY QUIET
MODULE 9
EVALUATINGOPTIONS
MODULE 10
FACT SHEETS
MODULE 11
TRAINING ANDINFORMATION
MODULE 12
PERSONALPROTECTION
ix
STRUCTURE OF THE CONTROL GUIDE
The control guide consists of a core and twelve modules.The core comprises five basic steps and provides anoverview of what is involved in organising a completenoise management programme. A short chapterexplains what is involved in each step.
The twelve modules provide supporting informationwhich can be drawn on in implementing each of thesteps. The flow chart on page xii illustrates theimplementation process and indicates the links betweenthe core and the modules. It also highlights the need toinvolve a range of people in the programme.
While the entire control guide is intended to be aresource accessible to everybody involved in theorganisation’s noise management programme, the tablebelow indicates which modules are most relevant tospecific functional sub-groups. The noise managerespecially will find all the modules useful in co-ordinating the programme and developing reports to, forexample, the chief executive officer, production engineerand health and safety committee.
Chief Production Maintenance Nurse/ Purchasing Employee Reps/Executive Engineering Staff Medical Staff OHS Committee
Module Officer Staff Staff
1 ✔ ✔ ✔
2 ✔ ✔ ✔
3 ✔ ✔
4 ✔
5 ✔ ✔
6 ✔ ✔
7 ✔ ✔ ✔
8 ✔ ✔
9 ✔
10 ✔ ✔ ✔ ✔ ✔ ✔
11 ✔ ✔
12 ✔ ✔
x
USING THE CONTROL GUIDE
The material in the guide can be approached in manydifferent ways, depending on the user’s needs. Thefollowing notes suggest how three key groups mightmost efficiently use the guide.
• Scan CORE pages 1 to 6 for overviews of yourorganisation’s legal obligations regarding noise andof the costs and benefits of managing noiseeffectively.
• Scan the Overview (page V).
• Scan CORE pages 14 to 16 for suggestions regardingdelegation of responsibilities for the programme.
• If time permits, scan other parts of the guide thatinterest you, especially modules 1, 6, 7 and 10.
• Delegate responsibility for detailed management ofthe noise management programme to anappropriate person (the guide refers to this personas the noise manager) and pass the guide on to thisperson with an indication of your personal supportfor the programme.
• Read through the entire core section to get a clearoverview before starting work on the programmeitself — if you set aside ten to fifteen minutes a day,this will take no more than two weeks.
• Arrange a meeting to inform and consult withothers who will be involved in or be affected by theprogramme (see ESTABLISH CONSULTATIVE PROCESS, pageCORE 8).
• As necessary, photocopy relevant modules andsections of the guide and distribute them to others(see the table on page ix).
• Systematically work through the programme steps(see the flow chart on page CORE xii for an overview),referring to specific modules as the need arises.
• Read Module 10: Fact Sheets for a general review ofthe effects of noise on hearing and approaches toprevention.
• Read Step 1 (CORE pages 1 to 6) for an overview of
CHIEFEXECUTIVEOFFICERS:
NOISEMANAGERS:
EMPLOYEE ANDHEALTH AND
SAFETYREPRESENT-
ATIVES:
xi
legal and other reasons your organisationshould tackle noise problems.
• Read Module 7: Noise Policy.
• As time permits, read modules 2, 5, 11 and 12for further information and ideas.
• Cooperate in the development of yourorganisation’s noise managementprogramme, using the guide as a generalreference.
xii
NOISE MANAGEMENT FLOW CHART
1 Establish aBasis forAction
2 Assessyourpresentposition
5 Monitor andEvaluate
Immediate
Short Term
MediumTerm
Ongoing
Nominate aNoise Manager
Establish aConsultativeProcess
Conduct a WalkThrough Audit
3 Set Goalsand Policies
4 Establish aNoiseManagementStrategy
Interim NoiseManagement
Implementobvious or simplecontrol measuresimmediately
Implement andupgrade hearingprotectionprogramme
Implement buyquiet programme
Implementnoise controlplan
Implement hearingprotectionprogramme
Time Frame Programme Steps (see details in Core) Consultation Module Reference
Inform all levels ofmanagementAdvise employeerepresentatives
1 Case Studies6 Costs/Benefits10 Fact Sheets
Evaluate presentMeasures
Conduct aNoise Survey
OHS Committeeand EmployeeRepresentatives
Noise committeeor equivalentformalmechanism
Noise committeeor equivalent
All managers,supervisors,employees
7 Noise Policy
3 In-house noiseControl
8 Buy Quiet9 Evaluating
Options11 Training and
Information
Consult throughexistingmechanism, (e.g.OHS Committee.Employee Reps)
Report/recommend toseniormanagement
Inform/involvesupervisors andworkers inassessments
Considerformalisingconsultativemechanisms (e.g.establish noisecommittee)
2 Walk ThroughAudit
4 Consultants
5 Using Surveys
11 Training andInformation
12 PersonalProtection
CORE 1
STEP 1: ESTABLISH A BASIS FOR ACTION
Your organisation needs a noise managementprogramme because noise problems won’t go away if youignore them. If anything, they are likely to get worse.
To deal with noise problems, you need to follow asystematic sequence of steps. The purpose of this guideis to lead you through those steps.
The guide consistently uses standard terminology whichis explained in Appendix l: Glossary of Technical Termsand Appendix 2: Measures of Noise Exposure. Spendsome time reading these and refer to them regularlyuntil you are well acquainted with the terms.
The Health and Safety in Employment Act 1992 and theHealth and Safety in Employment Regulations requirethe control of the exposure of people to noise at work.You should obtain a copy of this legislation. Appendix 3:Directory of Products and Services gives details of whereyou can obtain a copy.
Generally the legislation requires employers to protectemployees from excessive noise exposure by:
• quietening plant and equipment;
• reducing the amount of time individuals spend in highnoise levels;
• providing hearing protectors and appropriate trainingfor people working in areas that have not yet beenquietened.
Generally the legislation requires employees to:
• use any noise control equipment provided in theworkplace;
• wear personal hearing protectors in noisy areas.
INTRODUCTION
WHAT DOESTHE LAW SAY?
CORE 2
The following effects of noise have serious implicationsfor individuals and organisations.
Too much noise causes permanent hearing damage and areduced quality of life. There is no remedial medicaltreatment and hearing aids are of very limited benefit.
The most serious effect is impairment of the ability totake part in conversations and discussions. Enjoymentof television, radio and films is reduced. Socialwithdrawal and feelings of isolation can result, especiallywhen hearing deteriorates even further as a result ofageing.
Many people with noise-induced hearing impairmentalso suffer from tinnitus — ringing, buzzing or roaringsounds in their ears. These sounds, audible only to anaffected person, can be extremely disturbing and caninterfere with sleep.
Noise can be a safety hazard. It can distract attention. Itcan drown out the sound of a malfunctioning machine,an alarm signal or a warning shout.
Many people find that noise adds to the fatigue of workand makes it difficult to concentrate. Productivity cansuffer as a result.
Trying to understand speech in noisy surroundingsrequires extra concentration and strain. Messages orinstructions can be misunderstood. This can createconfusion, frustration and safety problems. Constantshouting to be heard above noise can lead to throatirritation.
Noise is a common source of annoyance and stress. Ithas been found in workplace surveys that noise is oftenthe chief complaint workers have about their workingconditions.
Additional information on the effects of noise arecontained in Module 10: Fact Sheets.
WHAT HARMDOES NOISE
DO?
HEARINGLOSS
TINNITUS
SAFETY
ANNOYANCEAND STRESS
COMMUNICATIONPROBLEM
FATIGUE/LOWPRODUCTIVITY
CORE 3
Failing to act on the problem of noise increases the risk ofhearing damage and increases costs as outlined below.
There are now heavy penalties under the Health and Safetyin Employment Act 1992 for failing to provide a safe placeof work and for breaches of the noise regulations.
Employees can lodge a claim for compensation with theACC for hearing damage caused by noise at work, whichwill have consequential financial penalties for theorganisation.
Other possible costs arise from accidents caused indirectlyby a noisy working environment.
Loss of productivity results from:
• errors in work caused through instructions not beingheard or properly understood;
• an inability to concentrate in a noisy environment;
• increased absenteeism;
• increased turnover with associated costs of recruitingand training replacement personnel;
• difficulty in competing for highly skilled staff because ofunattractive working conditions.
Rehabilitation costs may result if an employee needs to berelocated and retrained.
Module 6: Costs/Benefits provide a more detailed analysisof the costs associated with occupational noise exposure.The results are summarised below:
Source of cost Estimated annual costper noise exposed employee
Insurance $130
Absenteeism $570
Turnover $100
Employee quality $330
Productivity $660
Personal protection programme $90
Total Cost $1,880
WHAT IF WEDON’T DO
ANYTHING?
PENALTIES
OTHERCOSTS
ACC CLAIMS
CORE 4
If noise levels are hazardous to the health of employees,management must take action. Some common rules ofthumb for managers wanting to estimate whetherpotentially hazardous noise levels exist in their workplacesare:
• If noise levels are as loud as or louder than heavy citytraffic;
• If voices have to be raised to communicate with some-one about 1 metre away;
• If people who have worked in the noise for a while seemto be a bit deaf.
Perhaps hearing protectors have been issued to everyonein noisy areas. Isn’t that enough? Simply making hearingprotectors available is not enough! The most effectivenoise control is applied at source, and even whereprotectors are used as an interim measure they should beaccompanied by comprehensive consultation, informationand maintenance.
Perhaps your organisation has managed to reduce noiselevels so that no one’s daily noise exposure level exceeds 85dB(A) (the maximum permissible exposure). Isn’t thatenough?
Scientific studies in noisy industries show that asignificant risk of hearing damage remains even whendaily noise exposures are reduced to an 8-hour average of85 dB(A). Authorities such as the InternationalOrganisation for Standardisation (ISO) (through ISOInternational Standard 1999) claim that risk becomesnegligible only when exposures are reduced to 75 - 80dB(A).
The lowering of the maximum permissible exposure levelto 85 dB(A) is under consideration by a number of Statesin Australia. It is the maximum recommended by theNational Health and Medical Research Council. It is alsothe level specified in regulations in New Zealand, theUnited States of America, United Kingdom and Europe.Many Australian organisations have already adopted thislevel. Noise exposures should be reduced to the lowestlevel practicable below 85 dB(A).
HAVEN’TWE DONEENOUGH
ALREADY?
CORE 5
This control guide sets out a number of steps for theeffective management of noise. Indicative costs associatedwith some of the activities are outlined below.
A comprehensive noise survey, with recommendations, willcost $800 or more, depending on the size and complexityof the workplace.
Types of engineering controls vary greatly and so do theircosts. Straightforward and relatively inexpensivetreatments can often make the difference betweenhazardous and non-hazardous noise exposures.
Australian case studies (see Module 1: Case Studies fordetails) highlight the potential for significant noisereduction for minimal financial outlay. For example,Johnson & Johnson Pty Ltd. were able to reduce noiselevels in their Cotton Buds® making machines from 92dB(A) to 84 dB(A) by lining the inner faces of metalenclosures with a marine noise reducing material. Totalcost per machine was $500.
Waratah Wire Products took noise levels into accountwhen purchasing new barbed wire making machines. Thenew machines were supplied with a complete enclosureand a sliding opening to allow full access. Noise levelswere reduced from 98 dB(A) to 82 dB(A), with the costbeing included in the price of the machine.
Examples of other such cases taken from the Health andSafety Executive (UK) publication, 100 PracticalApplications of Noise Reduction Methods (HMSO, London,1983) are shown in the following table:
Problem Noise Level (dB(A))machine Control method Before After Cost
Paper reeler replace steel with bronze gears 99 86 $825
Paper cutter replace steel with plastic gear 93 85 $275
Plastic grinder redesign feed hopper 95 83 $110
Book binder line case guard with polyurethane 95 85 $45
Grinder replace steel with plastic exit chute 92 82 50% less
Band saw enclose in acoustic curtains 101 91 $2,500
WHAT DOESIT COST TODEAL WITH
NOISE?
ENGINEERINGCONTROLS
NOISE SURVEY
CORE 6
Work done to control noise can also pay off in other ways.For example, analysing sources of excessive noise anddesigning engineering controls often revealsopportunities to improve the operational capabilities ofmachines or processes. To take another example,reducing noise by lining the underside of a roof or ceilingwith reflective-coated sound-absorbent material couldimprove lighting and thermal comfort at the same time.
Hearing protectors Cost
Earmuffs per pair $9.00 - $60.00
Earplugs per pair
- Reusable $1.80 - $10.00
- Disposable $0.40 - $1.00(new each day)
Maintenance and Replacement Costs
Varies a great deal depending on the protector purchased.Average earmuff life may be 6 months to 2 years, andreusable earplug life 3 - 6 months.
Signposting
A typical “Hearing Protectors Area” sign (required byregulations) could cost $30 - $60.
Training and Education
Typical cost per hour of hiring a trainer: $50 - $100.
Expenditure on the management of noise is aninvestment that will:
• ensure responsible occupational health and safetypractice in your workplace;
• help meet your legal obligations;
• reduce your liability through compensation claims;
• make for a safer, more productive, more pleasantworking environment;
• reduce the likelihood of employees suffering hearingloss;
• enhance the image of your company because it actsresponsibly towards its employees.
PERSONALHEARING
PROTECTION
CONCLUSION
CORE 7
NOMINATEA “NOISE
MANAGER”
STEP 2: ASSESS YOUR PRESENT
A noise management programme requires carefulplanning, that is, the development of a noisemanagement strategy which is tailored to the specificneeds of the organisation. Its implementation requiresthe coordination of a number of activities. A “noisemanager” should be nominated to perform this role,check that the steps described in this control guide areworked through and that the necessary work iscoordinated.
If the organisation is small, this coordinating role couldbe carried out by the chief executive officer.
In a larger organisation, the role of coordinator could bedelegated to the safety manager (if there is one) or to anappropriate line manager such as a production engineeror workshop manager.
A still larger organisation may require separatecoordinators for different parts of the programme (forexample, noise control and personal protection), with asenior manager or committee overseeing broad directionand coordination.
Whatever the size of the organisation, the chief executiveofficer should appoint one or more senior managers to:
• provide a report to management which assesses theproblem and proposes a strategy (an outline of such areport is provided in Module 11: Training and Infor-mation);
• ensure that a noise policy is developed, publicised andimplemented;
• coordinate the development of the strategy and theday-to-day operation of the noise management pro-gramme;
• keep senior management informed of progress andproblems.
Everyone in the organisation should be informed whothe noise manager is, either by word of mouth, notice orstaff circular.
POSITION
CORE 8
The Health and Safety in Employment Act 1992 includesa requirement for employee consultation andcooperation.
Employee consultation and cooperation makes goodsense. Employees know their machines well and canoften make practical suggestions about reducing noisewithout interfering with the function of the machine.
Direct involvement of employees in the development ofthe noise management strategy also helps buildcommitment to its implementation.
Others who should be consulted are managers,supervisors, health and safety representatives andemployee representatives.
One of the noise manager’s first tasks should be toarrange for these groups to be informed and consulted.This may be done initially through existing consultativemechanisms (for example, the occupational health andsafety committee) or informal communication channels.However, once the problem has been assessed asrequiring long-term management, the noise managermay recommend the establishment of a special noisecommittee or task force.
In large organisations, such a committee could be asubcommittee of the health and safety committee. In asmall organisation it may be sufficient simply to hold ameeting, tell employees that a noise managementprogramme is to be set up and invite their comments andparticipation in its development.
A walk-through audit or assessment of noise sources,possible noise controls and management measures toreduce noise exposure can help to define the noiseproblem and provide the basis for a noise control plan.
The objectives are to:
• identify problem noise areas/machines;
• identify obvious noise control methods;
• evaluate the effects of major changes expected in theworkplace;
• identify the need for a detailed noise control study ordesign.
ESTABLISH ACONSULTATIVE
PROCESS
CONDUCTA WALK-
THROUGHAUDIT
CORE 9
The assessment should involve people familiar with thework processes as well as management: some of the bestnoise control solutions are generated on the shop floor.
The assessment should be coordinated by the noisemanager and documented as it proceeds.
Module 2: Walk-through Audit sets out a procedure for awalk through audit of the workplace.
As an adjunct to the walk-through audit, theeffectiveness of measures already in place to reduce noiseexposure or protect hearing should be evaluated.
Assess the effectiveness of:
• existing noise control treatments (e.g. enclosuredoors and linings);
• administrative measures to reduce noise exposure(e.g. job rotation arrangements);
• the personal hearing protection programme (e.g. theuse and condition of personal hearing protectors);
• noise information (e.g. do the employees know whatnoise levels they are exposed to and when and whereto wear personal hearing protection? Are noisy areassignposted and noisy portable equipment labelled?)
Where the walk-through audit identifies simple solutionsto noise problems (e.g. lining a component bin withrubber), arrange for these changes to be implemented asquickly as possible. If there are problems with existingcontrol measures and hearing protection programmes,initiate action to improve performance while the morecomprehensive programme is being developed.
The Health and Safety in Employment Regulationsrequire that, where an employee is or may be exposed toan hazardous level of noise, the employer is required totake all practical steps to ensure that the noise hazard iseliminated. In order to facilitate this, a noise surveyshould be conducted in premises where noise exposuresare likely to be hazardous to determine the extent of theproblem. Where a noise hazard is known to exist,
EVALUATEPRESENT
MEASURES
INTERIMNOISE
MANAGEMENT
CONDUCT ANOISE
SURVEY
CORE 10
suitable interim personal protection must be madeavailable to exposed employees.
A noise survey report is primarily a basis for action. Itshould not be seen as a menu for personal hearingprotectors, as though this were the end point of noisemanagement.
The noise survey differs from the walk-through noiseaudit in degree and precision. The walk-through auditand subsequent interim noise management action areuseful preliminary activities to commissioning a noisesurvey. By dealing first with problems that are easilyfixed, you will be able to have the more comprehensivenoise survey concentrate on the more difficult noiseproblems.
The noise survey provides basic technical informationabout the workplace to enable you to:
• Set noise control priorities by:
- identifying which employees are exposed to noiseabove the target exposure goal;
- identifying which areas and operations pose thegreatest risk.
• Provide relevant information to managers and employ-ees on noise in the workplace (e.g. by labelling noisyareas and equipment, charts summarising results, andtraining programmes).
• Select a range of appropriate hearing protectors foremployees in noisy areas.
• Define any further statutory obligations which mayhave to be fulfilled. For example:
- keep a copy of the survey on file,
- communicate results to employees,
- repeat the noise survey in say five years.
• Evaluate the success of your noise managementstrategy by comparing successive noise surveys.
Many organisations will engage consultants to undertaketheir noise survey (see Module 4: Consultants). It isworthwhile requesting the consultant to go beyond whatis normally provided in a noise report of this kind. Askthem to provide the information in a user-friendly formwith conclusions and, where appropriate,
CORE 11
recommendations in each of the areas specified above. Awell-chosen consultant should recommend specificcontrol solutions for the most pressing noise problems.
Module 5: Using Surveys provides further details on theuse and interpretation of noise surveys.
CORE 12
STEP 3: SET GOALS AND POLICIES
A noise policy lays down the general rules anorganisation intends to follow in dealing with its noiseproblems.
Policy decisions which set noise exposure goals, specificresponsibilities for managers, supervisors and employees,and preferred methods of dealing with the problem areneeded to underpin the noise management strategy.
Full consultation with employees is essential for thedevelopment of noise policy. In medium to largeorganisations, this is best achieved through a formalworkplace health and safety committee includingemployee health and safety representatives.
A noise exposure goal will provide a baseline againstwhich progress in noise control and buy quietprogrammes can be measured and evaluated.
Legislation currently specifies noise exposure limits — anoise exposure level, LAeq,8h of 85 dB(A) and a peak level of140 dB. However, organisations should seriouslyconsider adopting a goal lower than the currentlegislative requirements to:
• anticipate possible changes to legislation;
• take advantage of the health, safety and economicbenefits of lower noise levels
Set up a system to ensure that, wherever possible, theorganisation does not buy more noise than it already has.
Because noise control can be more effectively dealt withat the design stage, buying quiet is almost invariablybetter and cheaper than trying to control noise oncemachinery is installed. Quiet machines are often betterdesigned, better made and more reliable.
Specify a maximum acceptable noise level for newmachinery. This level will usually need to besignificantly lower than the noise exposure goal for theworking environment to allow for the addition of thenoise of the new machine to the existing noise levels onsite.
INTRODUCTION
POLICY ISSUES
NOISE EXPOSUREGOAL
BUY QUIET
CORE 13
It is also necessary to take account of additional noiseeffects when more than one machine is purchased for thesame work area. Generally, two identical machinesworking near one another will make about 3 dB(A) morenoise than either one alone; four machines will make upto 6 dB(A) more. To keep the total noise level of fourmachines below 80 dB(A), the noise level of individualmachines would have to be no more than 74 dB(A).
The preferred approach to noise management, asreflected in the Health and Safety in Employment Act, isbased on a hierarchy of controls: reduce noise levels asfar as possible; if there is still a problem then reduceexposure duration as far as possible; and if a problem stillremains, as an interim measure supply personal hearingprotectors, backed up by appropriate training andeducation.
While some inexpensive control options can beimmediately implemented, many noise problems will besolved only through medium- and long-term planningand budgeting. Consider allocating a budget each yearfor noise control.
Effective protection requires a properly managed andmaintained personal protection programme. Someonein the organisation should be trained to take the role ofhearing protector expert.
Employees working in noisy areas should be informed ofthe noise levels and their potential effects, provided witha choice of effective hearing protectors and with trainingin how to fit and wear them.
Employees at risk must be required to wear hearingprotection supplied to them and encouraged to do sothrough supervisors, fellow workers and training andinformation programmes.
Visitors to noisy areas, including employees from otherparts of the plant, should be issued temporarily withhearing protectors and requested to wear them.
Managerial staff should set an example. Few peopleactually enjoy wearing hearing protectors and ifmanagerial staff are allowed to walk through noisy areasunprotected, some employees will oppose wearing
NOISE CONTROL
PERSONALPROTECTION
CORE 14
hearing protectors themselves on the basis that what isgood enough for managers is good enough for them.
If noise management is to be effective, everyoneconcerned needs to know the areas they are responsiblefor and what they have to do to carry out theirresponsibilities.
This information should be written down in jobdescriptions or duty statements so that people have apermanent record to which they can refer.
A suggested division of responsibilities, appropriate for amedium-sized organisation, is shown below. Thearrangement is flexible. In smaller organisations oneperson may have to take on more than one of the roleslisted but in larger organisations some roles could beshared by several people.
The important point is to ensure that someone is clearlyresponsible for each of the listed functions.
NOTE: Managerial and legal responsibility for dealingwith an organisation’s noise problems rests with itssenior management. Senior management backing isvital to the success of a noise management programme.
The chief executive officer should:
• Accept personal responsibility for co-ordinating thenoise management programme (smaller organisations)or delegate this responsibility to a designated noisemanager (larger organisations);
• Approve and publicise the organisation’s noise man-agement policy;
• Plan for the ultimate elimination of hazardous noisefrom the organisation’s working environment;
• Approve a reasonable allocation of money for noisecontrol in each year’s budget;
• Ensure that appropriate management systems areestablished. In particular, ensure that everyone in-volved in the noise management programme knowswhat their responsibilities are, preferably by means ofa written notice, job description or duty statement;
CHIEFEXECUTIVE
OFFICER
RESPONSIBILITIESAND
OBLIGATIONS
CORE 15
• Set up management reporting systems. For example,require the occupational health and safety committeeto review the noise programme at least quarterly, andthe noise manager to submit a quarterly report tosenior management.
• Ensure that responsibility is built into the purchasingsystem by requiring that anyone approving the pur-chase of potentially noisy machinery must eithercertify that it is the quietest available or else justify thepurchase.
The noise manager should:
• Consult with workers, other managers, supervisors,health and safety personnel, and others as appropriate,and develop a noise management policy for approvalby senior management;
• Be a reference point for information about the noisepolicy and coordinate its implementation;
• Monitor noise control measures.
The purchasing department should:
• Advise all purchasing staff of the existence of the buyquiet policy;
• Develop and implement an approval procedure forensuring that noise is taken into account in thepurchase of all plant, equipment and powered tools.
A hearing protector expert should:
• Become a reference point for information and exper-tise on the correct use of hearing protectors;
• Monitor hearing protector use and rectify problems;
• Establish a hearing protector maintenance pro-gramme.
Supervisors should:
• Make sure employees know how to use the engineer-ing noise controls, know which areas and equipment
SUPERVISORS
HEARINGPROTECTOR
EXPERT
PURCHASINGDEPARTMENT
NOISEMANAGER
CORE 16
are noisy and ensure that employees in them aresupplied with hearing protectors and adequate train-ing;
• Set an example by wearing hearing protectors them-selves;
• Make suggestions for the engineering control of noise.
Workers should:
• Participate in workplace consultation on noise control;
• Use the engineering controls where installed;
• Wear hearing protectors in noisy areas;
• Report faults in engineering controls and hearingprotectors;
• Participate in training and contribute to the noisemanagement strategy.
Employee representatives should:
• Represent the views of workers to management and onoccupational health and safety committees;
• Report to workers on the progress in formulating thenoise management strategy and implementing theprogramme.
EMPLOYEEREPRESENTATIVES
WORKERS
CORE 17
STEP 4: ESTABLISH A NOISEMANAGEMENT STRATEGY
A noise management strategy needs to be tailored to theneeds of the organisation. Key elements of a noisemanagement strategy are buying quiet equipment, noisecontrol and personal hearing protection. Some of thefactors influencing its design include:
• Existing noise levels;
• Economic environment of the organisation, that is,budget, production and resource constraints;
• Availability of solutions for identified noise problems;
• Negotiations with employee representives or pressurefrom the occupational health and safety committee orhealth and safety inspector;
• Future plans for the expansion or contraction of theorganisation’s activities.
The consultative process will play an important role inachieving a workable strategy.
A buy quiet programme requires the integration of a setof procedures with the organisation’s establishedpurchasing arrangements. Write a “buy quiet” circularto inform everyone who buys new machinery for theorganisation to take noise into account. Don’t overlookpowered hand tools which are major noise sources inmany workplaces.
An outline of buy quiet procedures provided below isbased on categorising a purchase as minor or major.Module 8: Buy Quiet provides a more detailedtreatment.
For minor purchases:
• Ask equipment suppliers to provide noise emissioninformation.
• Use this information to compare brands and short-liston the basis of cost, technical specifications, noise
STEP 4: ESTABLISH A
INTRODUCTION
BUY QUIETPROGRAMME
MINORPURCHASES
CORE 18
emission and other safety requirements such as guard-ing.
• If possible, check the noise information by trialingshort-listed equipment under typical operating condi-tions (for example, router cutting hardwood with atungsten carbide bit) and select the one which doesthe job effectively with the least noise.
• Where possible, use noise measuring equipment at theposition of the operator’s ear. If measuring equipmentis not available, use systematic observer comparisonsto identify major differences in noise output.
• If the impact on the workplace noise environment islikely to be high and the cost of the equipment war-rants it, consider using a more controlled, comprehen-sive noise measurement procedure. If in-house exper-tise is not available, hire a noise consultant to under-take an assessment of the short-listed items and rankthem on the basis of noise emission
For major purchases:
• Specify a noise level range from “most desirable” to“acceptable”, in tender specifications.
• Include noise level testing in normal pre-purchasetesting procedures and trialing. If noise levels areunacceptable, ask the manufacturer to install furthernoise control measures.
• Re-test equipment for noise level during commission-ing and if necessary implement noise reduction meas-ures (for example, acoustic treatment of the workarea).
NOTE: While the decision to regard an equipmentpurchase as minor is normally made on the basis of lowcost per item, consider whether the equipment should beregarded as a major purchase, based on an assessment ofits likely impact on noise levels in the workplace. Thefollowing factors, as well as cost, should be taken intoaccount:
• Existing noise levels in the workplace;
• Amount of daily usage;
• Number of these items to be purchased now or in thefuture.
MAJORPURCHASES
CORE 19
Regional offices of an organisation purchased chainsawsin small quantities for medium duty shrub and treelopping applications. As the number purchased for theorganisation as a whole was considerable, the centraloffice decided to undertake an evaluation of all availablechainsaws to establish the best and quietest option forpurchase. Among the many chainsaws which weretechnically acceptable, the noise level varied by as muchas 10 dB(A). The relative price range was much smaller.One of the cheapest was also the quietest.
The noise policy (Step 3) will have established noiseexposure goals for your workplace (or workplaces). Inmany organisations noise problems are complex and theachievement of goals may take some years. Theinformation gathered (in Step 2) may also havehighlighted a number of options for noise control. Theseoptions will need to be evaluated to assess their costs andbenefits and a time frame developed in which the mosteffective measures can be carried out. This is noisecontrol planning, and it needs to be integrated with theoverall direction, productivity and financial planning ofthe organisation.
The noise manager should be able to specify a series ofoptions for noise control in the workplace. For example:
Option 1: Replace machines A and B
Option 2: Enclose machines A and B
Option 3: Treat the area around machines A to F forreverberation by the use of acoustic screenstogether with absorptive lining of thebuilding.
If it is difficult to identify options for noise control, thismay be a good time to call together relevant people inthe organisation. These may include engineering,maintenance, production and health and safetypersonnel. Look at the results of the walk-through auditand discuss the options. It may also be the right time toinvolve an acoustical consultant who may be aware offurther options.
NOISECONTROL
PLAN
IDENTIFYBROAD NOISE
CONTROLOPTIONS
NOISECONTROL
ADVICE
AN EXAMPLE
CORE 20
The three main services for which you may find aconsultant beneficial are to:
• obtain a detailed noise diagnosis to assess the sourcesof noise and potential for noise reduction;
• identify and evaluate the most cost-effective optionsfor noise control;
• receive a detailed design of treatments for the pre-ferred option and to supervise contractors.
The above services could be provided for either anexisting plant or a proposed plant.
Where notification to reduce noise levels has been issued,the consultant may also liaise with the Health and SafetyInspector on the organisation’s behalf.
A consultant may therefore be involved at several stagesduring the implementation of the noise managementstrategy. The following aspects of your involvement witha consultant are important.
Choice of consultant
You will need someone with appropriate instrumentationto diagnose the problems, and have experience in yourtype of industry or machinery.
Setting up the brief
You will get the best from your consultant by knowingwhat to ask them to do and by knowing what to expect.
Consultants and contractors
It is helpful to understand the role of a consultant(provider of expertise) versus that of a contractor(provider of skill).
Module 4: Consultants looks at these issues to enableyou to “get the best from consultants and contractors”.
The Safety and Health Accumulated Research Experience(SHARE) aims to identify successful solutions tocommon health and safety problems and promotewidespread application of these solutions in workplaces.The SHARE registry may be able to help you find anexisting solution used by another company for a similarproblem. Copies of SHARE solutions in noise areavailable from:
ADDITIONALRESOURCE
CORE 21
The Victorian Department of LabourPublic Relations and Information BranchLevel 22, Nauru House,80 Collins Street,62 The TerraceMELBOURNE VIC 3000Telephone (+61 3) 655 6332
Occupational Safety and Health ServiceDepartment of LabourPO Box 370562 The TerraceWELLINGTONTelephone (04) 471 2937.
Having identified some options for noise controlstrategies, it is in the organisation’s interest to carefullyevaluate the costs and benefits of each option. Costs andbenefits of noise control can be in both dollar and non-dollar terms. Some approaches to evaluating theeffectiveness of various noise control options are set outin Module 9: Evaluating Options.
There may be either costs or benefits to productionwhich may increase with new machinery or maydecrease if a machine is slowed down or enclosed.
Similarly, there may be either costs or benefits toproduct quality. While this would normally increasewith new, quieter technology, some decrease withinacceptable limits may be allowed in the interests of noisecontrol.
Some of the considerations are summarised in the tablebelow.
CostsTo treat or replace machinesCost per decibel reductionCost per worker down-time during installationCost of training workers in noise reduction technologyCost of maintenance of noise controlsExtra cost of purchasing quieter machinery
BenefitsCost reduction due to hearing loss claimsCost reduction in personal hearing protection/educationprogrammeImproved safetyImproved verbal communication possibleBetter working relationsReduced vibration exposure of workers possibleReduced environmental noiseLess discomfort from personal hearing protectionLower worker stress, increased productivityImproved thermal environment possible
EVALUATINGCOST/
BENEFITS FORNOISE
CONTROL
CORE 22
To identify the most cost-effective option, the broadoptions for noise control can be evaluated against thecost/benefit criteria given above. Gathering theinformation for the cost-benefit analysis will requireinput from a range of people in the organisation, fromengineering to personnel to production. This processcould be coordinated by the noise manager.
While the above processes are taking place in theplanning of major noise controls, it is crucial that thecontinuing maintenance/modification/upgradingactivities are also fitted into the noise control plan.
In the walk-through audit, problems such as loose orworn parts, machine imbalances and missing silencersmay have been identified. These are matters for normalmaintenance.
“Add-ons” (for example, a noisy blower added to clean aconveyor) may also have been installed withoutconsideration of noise. Other machines may have beenspeeded up to increase production, thereby causing anoise hazard. These modifications and upgrades canoccur without reference to any overall noise planning,resulting in a gradual increase in noise levels over aperiod of time.
Consider the need to:
• establish a maintenance regime specifically aimed atnoise control;
• train maintenance staff to recognise and correctsimple noise problems and carry out minor modifica-tion/upgrades so as not to increase noise levels overall;
• introduce a “condition monitoring” programme todetect possible machinery faults before they become anoise hazard and ultimately cause a breakdown;
Module 3: In-House Control provides information formaintenance staff to establish these procedures andperform in-house noise control.
Until noise is reduced to non-hazardous levels by meansof engineering controls, individual workers must beprotected by using personal hearing protectors.
PERSONALPROTECTIONPROGRAMME
ONGOINGMAINTENANCE,MODIFICATION,
UPGRADINGOF PLANT
CORE 23
It is not enough simply to buy hearing protectors andhand them out. Effective protection requires a properlymanaged personal protection programme. The key stepsare outlined in the following subsections.
Provide information to employees who are likely to beexposed, about:
• the harmful effects of high noise levels, especiallypermanent hearing impairment and permanent ring-ing in the ears;
• the organisation’s short-term and long-term plans forreducing noise exposures to non-hazardous levels;
• the organisation’s obligations to provide personalhearing protectors until the noise is reduced;
• the employee’s obligations to use hearing protectors inhazardous situations.
The use of a video is invaluable to demonstrate the effectsof noise mentioned in the first point above. Alternatively,hire a hearing protector supplier or safety firm thatspecialises in providing this kind of education.
Information on the remaining points listed above couldbe supplied at the same session by the noise manager orother appropriate staff member.
Mark areas where noise exposure levels exceed theorganisation’s exposure goal with signs indicating thathearing protectors must be worn. Standard signs areincluded in this kit (see also “Signs” in the Yellow Pages).
Label noisy power tools and portable equipment with asticker saying “Do not use unless wearing hearingprotectors”. To be on the safe side, regard as noisy anyitem capable of producing continuous noise levels greaterthan 85 dB(A) or peak noise levels exceeding 140 dB atthe operator’s ear.
For each individual, aim to buy protectors that:
• have been graded and have adequate noise reduction;
• are compatible with any other safety equipment theperson has to wear;
1. PROVIDEINFORMATION
2. IDENTIFYNOISY AREAS
ANDEQUIPMENT
3. SELECT ANDBUY HEARINGPROTECTORS
CORE 24
• are comfortable;
• fit properly;
• do not interfere with work.
When selecting hearing protectors:
• contact several suppliers, tell them about your noiseconditions and working environment and ask them forbrochures of the graded protectors they would recom-mend for your needs;
• make a short list of suitable protectors in consultationwith prospective wearers;
• ask suppliers to demonstrate the short-listed protec-tors, show the correct way of fitting them and answerquestions from prospective wearers;
• contact as many suppliers as necessary until everyonehas been fitted with a suitable device.
Wearers should be given a choice:
• between muffs and plugs (if they can get a good fitwith both, and where plugs are appropriate);
• between different brands or models of suitable muffsor plugs.
Both types can provide effective protection if properly used.The following table summarises the advantages anddisadvantages of each.
Earmuffs
Advantages Disadvantages
Easy to use Seal around ears can beimpaired by spectacleframes, hair and caps
Careful fitting not as Can get in the way of othercritical as with plugs headgear
Some protection likely Can interfere with hair styleeven if not used carefully
Can be used even if wearer Can be a nuisance in confinedhas a minor ear infection work space
Easy for supervisor to see Can be uncomfortable in hotthat they are being environmentsused properly
CORE 25
Earplugs
Advantages Disadvantages
Hair, glasses, earrings do May provide very littlenot impair seal protection if not used
carefully
Don’t get in the way of Problems if user getsother headgear hands dirty or wears
gloves
Don’t interfere with hair style Can’t be used if wearerhas an ear infection
Don’t get in the way in Can be difficult forconfined work spaces supervisor to see that
they are being usedproperly
Cool, easy to carry around
Arrange for the hearing protector supplier to providetraining when hearing protectors are first bought. If thesupplier cannot supply a training officer, ask for anyavailable printed information about correct use and careof the protectors.
Appoint a suitable staff member (for example, the noisemanager, nurse or health and safety officer) to becomethe local expert on hearing protectors. This personshould obtain, study and retain, for future reference, allinformation about all hearing protectors purchased bythe organisation.
Use the information provided with this control guide fortraining purposes. (This includes Module 10: FactSheets and material in Module 11: Training andInformation and Module 12: Personal Protection.)
Provide new employees in noisy areas with hearingprotectors and associated information and training aspart of their introduction to the organisation.
Regular inspection and maintenance of protectiveequipment highlights the seriousness of the noise issuewithin the organisation and helps maintain wearermotivation. It also provides opportunities for refreshertraining in correct use of equipment.
4. PROVIDETRAINING ON
USE AND CAREOF HEARINGPROTECTORS
5. ESTABLISH AMAINTENANCE
PROGRAMME
CORE 26
Through the maintenance programme:
• Make regular inspections of all hearing protectors (atleast monthly);
• Repair or replace defective protectors;
• Record all results for costing, budgeting and legalpurposes.
CORE 27
STEP 5: MONITOR AND EVALUATE
Evaluation is the careful appraisal of the planning,implementation, impact and outcomes of a programmeagainst its goals and objectives.
Evaluation enables the following assessments to be madeabout the organisation’s noise management programme:
• The extent to which the programme has met thetargets, goals and objectives;
• Whether resources are being effectively allocated(supporting bids for necessary resources);
• The need for changes in the direction of the pro-gramme.
Evaluation can also be a useful consultative tool.Feeding back the findings to management and otherswho have participated in both the evaluation and theprogrammes will generate further awareness andinvolvement.
The three sub-programmes of the noise managementstrategy, that is, the buy quiet programme, the noisecontrol plan and the hearing protection programme canbe monitored using the following checklist. It is ameans of checking that the programme is beingimplemented as planned. The detail will need to betailored to reflect the actual activities of yourorganisation’s noise management programme.
In addition to checking that all aspects of theprogramme have been implemented as planned,indicators need to be identified which will measure orgauge how well the planned measures have had theirdesired or planned effect. The details of such indicatorsneed to reflect the specific, detailed goals and plans ofeach organisation. Possible indicators for some of theactivities are listed below as examples.
INTRODUCTION
MONITORINGPROGRAMME
IMPLEMENTATION
EVALUATION
CORE 28
MONITORING CHECKLIST
General Programme Yes No Noise Control Yes No
Assessment 1. Noise control survey and1. Noise manager nominated ❐ ❐ report completed ❐ ❐
2. Walk-through survey 2. Major noise sourcescompleted ❐ ❐ identified ❐ ❐
3. Noise management proposal 3. Solutions to noiseforwarded to management ❐ ❐ problems documented ❐ ❐
4. Current noise control and 4. In-house maintenance andhearing protection activities upgrading programmesaudited ❐ ❐ address noise control ❐ ❐
5. Legal obligations established 5. Priorities set for noiseand met ❐ ❐ control ❐ ❐
6. Simple noise control 6. Budget and resourcessolutions are implemented allocated ❐ ❐immediately ❐ ❐
7. Appropriate consultative Buy Quiet Proceduresarrangements established ❐ ❐
1. Buy quiet policy andGoals and policies procedures developed ❐ ❐
8. Noise goals and policies 2. Relevant staff informeddeveloped ❐ ❐ and trained ❐ ❐
9. Policies circulated to all 3. Sample purchasingemployees ❐ ❐ specifications available ❐ ❐
Noise Management Strategy Hearing Protection Programme
1. Noise management strategy (detailed checklist in Module 12)
prepared ❐ ❐ 1. Noisy areas and equipment2. Budget and resources identified and signposted/
allocated ❐ ❐ labelled ❐ ❐
3 Individuals advised of their 2. Effective, wearer-acceptabletheir rights and hearing protectors issuedobligations ❐ ❐ to employees at risk ❐ ❐
4. Employees informed about 3. Wearing of hearingthe noise levels to which protectors monitoredthey are exposed ❐ ❐ and supported ❐ ❐
5. Training programmes 4. Training provided inestablished for key groups ❐ ❐ fitting and correct use ❐ ❐
6. Noise addressed in induction 5. Hearing protectorsand other relevant training maintained and replacedprogrammes ❐ ❐ as necessary ❐ ❐
7. Monitoring, reporting and 6. Reference point established evaluation processes for information and established ❐ ❐ advice ❐ ❐
CORE 29
Noise Strategy (General)
How close has the implementation of the three key sub-programmes of the noise strategy come to achieving thenoise exposure goal? Possible indicator:
• Monitor and check progress in reaching the noiseexposure goal. Carry out a noise survey every twoyears and compare to evaluate progress.
Is noise control at source being given priority over theuse of hearing protection? Possible indicators:
• Look at how much is being budgeted and spent onnoise control measures compared with personalprotection.
• List the noise control solutions which have beenimplemented.
Buy Quiet Programme
Are the buy quiet procedures being implemented?Possible indicators:
• New equipment tenders include noise level specifica-tions;
• Decisions taken to purchase specific items of equip-ment reflect consideration of noise levels;
• Requests to involve noise manager in equipmentassessment procedures.
Noise Control
Have options for the control of noisy machinery beendeveloped and implemented? Possible indicators:
• Priorities established for solving noise problemsassociated with specific work processes or equipment;
• Plans for equipment modifications developed;
• Equipment modifications installed.
Personal Protection
Are the hearing protectors being used effectively?Possible indicators:
• Individuals are equipped with protectors suitable forthem;
• Protectors are being worn correctly;
• Usage rates and condition of hearing protectors;
• Range of hearing protectors available.
CORE 30
Some organisations provide free hearing tests(audiometry) for their employees every year or two as afinal check on the effectiveness of their noise control andpersonal protection programmes, and to try to detectindividual cases of hearing loss at an early stage so thatsteps can be taken to prevent further damage.
Unless an organisation possesses both the necessaryequipment and expertise, it would be best to subcontracthearing tests to an appropriate consultant.
Specifications for audiometric equipment and proceduresare given in Australian Standard AS1269 (see Appendix 3:Directory of Products and Services).
Guidance in the assessment of audiograms is given in theNational Acoustic Laboratories Report No. 80, Criteriafor Assessing Hearing Conservation Audiograms, AGPS,Canberra, 1980.
A NOTE ONAUDIOMETRY
CORE 31
TERMS
Technically called sound pressure level; the physicalmagnitude or strength of noise: experienced by people asloudness.
The unit used to measure noise level. The pressurechanges of the loudest sounds we can hear are about10,000,000 times greater than those of the faintestsounds. Because a measurement scale ranging from 1 to10,000,000 is awkward to work with, scientists insteaduse the logarithmic decibel (dB) scale for measuring thestrength of sound.
By working with the logarithms of numbers rather thanthe numbers themselves, the decibel scale compresses a1 to 10 million range of pressures into a range of 0 to140 dB.
Because of the logarithmic nature of the decibel scale, anoise which is 3 dB higher in level than another hastwice as much energy; a noise 3 dB lower in level hashalf as much. A 10 dB difference in level corresponds toan energy ratio of 10; 20 dB corresponds to a ratio of100; 30 dB to 1,000; and so on.
A-weighted decibel. The “A” indicates that the noise hasbeen measured through a special acoustic filter whichis used to assess how hazardous the noise is forindividuals.
C-weighted decibel. The “C” indicates that the noise hasbeen measured through a special acoustic filter whichgives results that are used for selecting hearingprotectors in Australia.
The overall amount of noise to which a person isexposed. Noise exposure depends on both the noise leveland the exposure duration (the length of time spent inthe noise).
As explained in Appendix 2, two alternative terms areused for expressing the amount of a person’s daily noiseexposure at work: daily noise exposure level and dailynoise exposure.
APPENDIX 1: GLOSSARY OF TECHNICAL
Noise level:
dB or decibel:
Noiseexposure:
dB(C):
dB(A):
CORE 32
The protection of individuals from the harmful effects ofnoise by means of signposting noisy areas, arrangingeducation, providing individuals with appropriatehearing protectors and monitoring their use. Manypersonal protection programmes also include regularhearing checks.
The amount of noise reduction provided by a hearingprotector.
Personalhearing
protection:
Attenuation:
CORE 33
EXPOSURE
At present in New Zealand two alternative terms are usedfor expressing the amount of a person’s daily noiseexposure at work: daily noise exposure level and dailynoise exposure.
First of all, it is important to understand the differencebetween noise level and noise exposure level.
Noise level (symbol LAeq) is simply the strength orphysical magnitude of noise, expressed in dB(A) (whichstands for “A”-weighted decibels). For example the noiselevel of heavy traffic is about 85 dB(A).
Noise exposure level, on the other hand, is the totalamount of noise energy a person is exposed to in thecourse of their working day, expressed as an 8-houraverage (symbol LAeq,8h
). It takes account of both thenoise level and the length of time the person is exposedto it. To reach a noise exposure level of 85 dB(A), aperson would have to be exposed to a noise level of 85dB(A) for 8 hours (or to some other combination of noiselevel and exposure duration having the same totalenergy).
It is quite possible for the noise exposure level to be lessthan 85 dB(A) even though the noise level is greater than85 dB(A). This would happen, for example, if the onlynoisy machine in a factory created a noise level of 90dB(A) but people were exposed to it for only 2 hours aday. In this case the noise exposure level would be 84dB(A).
A rule known as the 3 dB rule is worth noting. The ruleis that when determining noise exposure level, halvingthe exposure duration is equivalent to decreasing thenoise level by 3 dB(A) and doubling the exposureduration is equivalent to increasing the noise level by 3dB(A). It follows from the 3 dB rule that thecombinations of noise level and exposure duration shownbelow all produce the same noise exposure level of 85dB(A):
APPENDIX 2: MEASURES OF NOISE
NOISE LEVEL
NOISEEXPOSURE
LEVEL(LAeq,8h)
CORE 34
82 dB(A) for 16 hours 91 dB(A) for 2 hours85 dB(A) for 8 hours 94 dB(A) for 1 hour88 dB(A) for 4 hours . . . and so on.
An operator may work at several different tasks, eachwith a different noise level, in the course of a workingday. A Partial Noise Exposure will be received from eachtask, depending on the amount of time spent on the taskand the associated noise level. Adding the Partial NoiseExposures together will give the operator’s Daily NoiseExposure.
The Approved Code of Practice for Management of Noisein the Workplace provides a table for determining thePartial Noise Exposure associated with any combinationof noise level and exposure duration. This is duplicatedbelow.
To determine an employee’s noise exposure level, thefollowing data are needed:
(a) The different noise levels to which the employee isexposed;
(b) The time that the employee is exposed to each ofthese noise levels.
Table 3 can be used to determine the LAeq,8h using the
following method:
• Convert each noise level to a Pascal-squared (Pa2)value.
• Multiply each Pa2 value by the respective exposuretime in hours.
• Add these resulting fractional exposures together, toobtain the total exposure.
• Divide the total exposure by 8, to obtain the 8-houraverage Pa2
• Convert this value of Pa2 using table 3 again to obtainthe LAeq,8h
This is the employee’s Daily Noise Exposure Level(LAeq,8h)
Table 3 can also be used to calculate any LAeq value, toconvert dose or exposure measurements to LAeq and viceversa, or to simply add and subtract noise levels.
PARTIALNOISE
EXPOSURE
CORE 35
Table 1: Typical Daily Noise Exposure Details for anEmployee
Machine/Process Measured Duration Pa2 Partialnoise level of (Using Noise
LAeq,T Exposure, T Table 3) Exposure(dB(A)) (Hours) (Pa2h)
Furnace 105 0.5 13 6.5
Chipping hammer 96 4.0 1.6 6.4
Power hacksaw 92 1.5 0.63 0.9
Welding 90 2.0 0.40 0.8
Daily Noise Exposure 14.6
The Daily Noise Exposure is thus 14.6 Pa2h, and thenoise exposure level is determined by dividing thisexposure by the 8 hours in a normal working day.
The average Pa2 value of this exposure is therefore 14.6/8= 1.8 Pa2
The noise exposure level or LAeq,8h is obtained by lookingup 1.8 in Table 3.
The noise exposure level or LAeq,8h is therefore 96.5 dB(A),which is normally rounded to the nearest whole number(0.5 is normally rounded up).
So LAeq,8h = 97 dB(A)
Daily Noise Exposure is an alternative way to express thetotal amount of noise energy to which a person isexposed over their working day. Noise Exposure isnormally expressed in “Pascal-squared hours” which hasthe symbol Pa2h.
A person’s Daily Noise Exposure is therefore simply thenumber of Pa2h that they are exposed to in a workingday, however long the day is. The noise exposure is thecombination of noise level and duration of exposure tothat level.
The relationship between Noise Exposure and NoiseExposure Level is shown in table 2 below:
AnExample:
DAILYNOISE
EXPOSURE(Pa2h)
CORE 36
Noise Daily Noise Noise Daily NoiseExposure Exposure Exposure Exposure
Level (dB(A)) (Pa2h) Level, (dB(A)) (Pa2h)
80 0.32 98 2081 0.40 99 2582 0.51 100 3283 0.64 101 4084 0.80 102 5185 1.0 103 6486 1.3 104 8087 1.6 105 10088 2.0 106 13089 2.5 107 16090 3.2 108 20091 4.0 109 25092 5.1 110 32093 6.4 111 40094 8.0 112 51095 10 113 64096 13 114 80097 16 115 1000
TABLE 2:RELATIONSHIP
BETWEENNOISE
EXPOSURE ANDNOISE
EXPOSURE LEVEL
CORE 37
dB Pa2 dB Pa2 dB Pa2
75 0.013 95 1.3 115 130
75.5 0.014 95.5 1.4 115.5 140
76 0.016 96 1.6 116 160
76.5 0.018 96.5 1.8 116.5 180
77 0.020 97 2.0 117 200
77.5 0.023 97.5 2.3 117.5 230
78 0.025 98 2.5 118 250
78.5 0.028 98.5 2.8 118.5 280
79 0.032 99 3.2 119 320
79.5 0.036 99.5 3.6 119.5 360
80 0.040 100 4.0 120 400
80.5 0.045 100.5 4.5 120.5 450
81 0.050 101 5.0 121 500
81.5 0.057 101.5 5.7 121.5 570
82 0.063 102 6.3 122 630
82.5 0.071 102.5 7.1 122.5 710
83 0.080 103 8.0 123 800
83.5 0.090 103.5 9.0 123.5 900
84 0.10 104 10 124 1000
84.5 0.11 104.5 11 124.5 1100
85 0.13 105 13 125 1300
85.5 0.14 105.5 14 125.5 1400
86 0.16 106 16 126 1600
86.5 0.18 106.5 18 126.5 1800
87 0.20 107 20 127 2000
87.5 0.23 107.5 23 127.5 2300
88 0.25 108 25 128 2500
88.5 0.28 108.5 28 128.5 2800
89 0.32 109 32 129 3200
89.5 0.36 109.5 36 129.5 3600
90 0.40 110 40 130 4000
90.5 0.45 110.5 45 130.5 4500
91 0.50 111 50 131 5000
91.5 0.57 111.5 57 131.5 5700
92 0.63 112 63 132 6300
92.5 0.71 112.5 71 132.5 7100
93 0.80 113 80 133 8000
93.5 0.90 113.5 90 133.5 9000
94 1.0 114 100 134 10,000
94.5 1.1 114.5 110 134.5 11,000
The Pascal-squared values in the table above have been rounded to 2 significantfigures. This will result in an accuracy of at least ±5% or ±0.2 dB.
TABLE 3: DECIBEL TO PASCAL-SQUARED CONVERSION
CORE 38
This appendix is a general directory designed to helpusers locate technical expertise and the necessaryequipment and materials needed to implement aneffective noise management programme in theworkplace.
You should also check with your local OccupationalSafety & Health Branch Office since some may haveproduced local directories.
Technical Expertise
This directory will assist you in finding the people withthe following technical expertise you may need toimplement an effective noise management programme inyour workplace:
• Noise measurement and engineering noise control;
• Hearing tests.
Equipment and Materials
This directory will assist you in finding the followingequipment and materials you may need to implement aneffective noise management programme in yourworkplace:
• Noise control equipment and materials;
• Safety warning signs;
• Hearing protectors.
Legislation and Standards
This directory gives details of:
• Legislation on noise;
• Standards.
AND SERVICESAPPENDIX 3: DIRECTORY OF PRODUCTS
INTRODUCTION
CONTENTS
CORE 39
How do I know if I have a noise problem and how do Iget engineering advice about ways of reducing thenoise?
It is not always possible for people in workplaces to judgecorrectly whether a certain noise, or noises, constitute(s)a long-term hazard to employees. Consultants can assistby carrying out a noise survey. The survey will establishwhether a noise hazard exists. The consultant willgenerally offer advice on the results of the noise surveyfirstly by emphasising the most appropriate step, that is,engineering control of noise and vibration.
It is advisable to consult your relevant employer oremployee organisations as they may be able to offer aservice.
The Yellow Pages telephone directory is a good generalsource of information on consultants and services. Therelevant sections are “Acoustic Consultants”, “NoiseControl and Measurement” and “Occupational &Industrial Health & Safety”. “Vibration Analysis/Control”may also be relevant.
Where do I get information if I want hearing tests formy employees?
Audiologists are professionally qualified to test hearing.Audiometrists are able to do basic hearing tests but mayneed to refer their client to an audiologist or medicalspecialist if further assessment is necessary.
The Yellow Pages section “Audiologists” may be a sourceof information on audiometrists who would do screeninghearing tests.
An additional source of information would be the unionor employer association relevant to your industry.
How do I reduce the noise and where do I buyequipment, materials and services to reduce noise andvibration?
Many companies provide advice, services and specialproducts for reducing noise. Some companies may beable to offer noise measuring services as well as supplyand installation of controls. The following sources will
NOISEMEASUREMENT
ANDENGINEERING
CONTROL
HEARINGTESTS
NOISECONTROL
EQUIPMENTAND
MATERIALS
CORE 40
provide information on available engineering contractorsand suppliers of equipment and materials to absorb,insulate, damp, muffle or isolate vibration and noise inthe workplace:
• The Yellow Pages sections “Noise Control and Meas-urement”, “Acoustic Materials and Service”, “VibrationAnalysis / Control”, “Insulating Materials-Retail” and“Insulating Materials-Wholesale or Manufacturers”.
• The Australian Engineering Directory 1989 which canbe obtained from Technical Indexes Pty Ltd, in NSW,Victoria and Queensland, at a cost of A$95.00. Librar-ies may also hold copies of this publication.
• Advertisers in New Zealand Acoustics, the journal ofthe New Zealand Acoustical Society, also provide asource of information. This publication can be ob-tained from: The Secretary, New Zealand AcousticalSociety, PO Box 1181, AUCKLAND. University librariesmay also have copies of the publication.
How do I warn people that an area or machine is noisy?
The warning that hearing protectors are necessary in aspecific area can be presented on a sign with words only(verbal), with a picture only (pictograph), or with wordsand picture (verbal pictograph). It is important to ensurethat the sign can be understood by persons not familiarwith written English.
The New Zealand/Australian Standard NZ/AS 1319 detailsrules for the design and use of safety signs. This can beobtained from Standards New Zealand, Wellington.
Convenient signs you can use are included in theManagement of Noise at Work Resource Kit, availablefrom the Occupational Safety & Health Service. Thesesigns are in two sizes: A3 and A4, and are printed on adurable synthetic material. Write, in the spaces provided,the grade of hearing protector required and where peoplecan get the protectors from (see facing page). Additionalcopies of these signs are available from OSH.
The signs are also supplied as a smaller self-adhesivelabel which may be attached to noisy machines.
The Yellow Pages section “Signs” lists companies whichmay supply safety signs complying with the Standard.
SAFETYWARNING
SIGNS
CORE 41
Grade hearing protectionmust be worn. Obtain from
NOISE HAZARD AREA
Reducing the noise level is preferable, but in themeantime how do I protect and educate my employeesand where can I buy hearing protectors?
Reduction of the noise level is the best way of dealing witha noise problem. However, if noise reduction is delayed, itis essential to supply hearing protectors and training foreveryone involved and/or reduce the amount of timeindividuals spend in noisy areas, for example, having staffalternate between quiet and noisy areas.
Consultants who advise on hearing protectors andeducation are listed in the Yellow Pages in the “AcousticConsultants”, “Occupational & Industrial Health & Safety”and “Audiologists” sections.
The suppliers of hearing protectors are listed in the YellowPages under “Safety Equipment and Products” and“Clothing: Protective”. Some suppliers will give trainingsessions and advice on the choice and fit of hearingprotectors.
It is also advisable to consult your relevant employer andemployee organisations as they may be able to offer aservice.
The Occupational Safety & Health Service has apublication entitled List of Graded Hearing ProtectionDevices (which is also included in the Resource Kit).Copies can be obtained from OSH branch offices.
HEARINGPROTECTORS
Write in theappropriate
number
Write in wherethe protectors
can be obtainede.g. Stores Dept
Phil Smith
CORE 42
Where can I obtain information about noise legislationand standards?
Copies of the Health and Safety in Employment Act 1992and the Health and Safety in Employment Regulations1995 can be obtained from:
Your nearest OSH branch office or BennettsGovernment Books
Standards can be obtained from:
Standards New ZealandPrivate Bag 2439Standards House155 The TerraceWELLINGTON 6001Tel: (04) 498 5990
Sales Orders (04) 498 5991Standards Information Service 0900 50 550Quality & Certification (04) 498 5993Facsimile (04) 498 5994
Relevant Standards include:
IEC 651-1979 Sound level meters
IEC 225-1966 Octave, half-octave and third-octave bandfilters intended for the analysis of sounds and vibrations
IEC 804-1985 Integrating-averaging sound level meters
ISO 1999-1990 Acoustics - Determination ofoccupational noise exposure and estimation of noiseinduced hearing impairment
ISO 2631-1985 Evaluation of human exposure to wholebody vibration (Parts 1-3)
ISO 4869-1990 Acoustics - Hearing protectors
ISO 5349-1986 Mechanical vibration - Guidelines for themeasurement and the assessment of human exposure tohand-transmitted vibration
BS 6841-1987 Measurement and evaluation of humanexposure to whole-body mechanical vibration andrepeated shock
AS 1081-1990 Acoustics - Measurement of airborne noiseemitted by rotating electrical machinery
AS 1217-1985 Acoustics - Determination of sound powerlevels of noise sources (Parts 1-7)
NOISELEGISLATION
ANDSTANDARDS
CORE 43
AS 1259-1990 Acoustics - Sound level meters
AS 1269-1989 Acoustics - Hearing Conservation
AS 1276-1979 Methods for determination of sound classand noise isolation class of building partitions
NZ/AS 1319-1994 Safety signs for the occupationalenvironment
AS 1359.51-1986 Noise level limits (IEC 34-9)
AS 1591-1987 Acoustics - Instrumentation foraudiometry (See also Z43)
AS 1633-1985 Acoustics - Glossary of terms and relatedsymbols
AS 1807.16-1989 Determination of sound level incleanrooms
AS 1807.20-1989 Determination of sound level atinstalled workstations and safety cabinets
AS 1948-1987 Acoustics - Measurement of airbornenoise on board vessels and offshore platforms
AS 2012-1990 Acoustics - Measurement of airbornenoise emitted by earth-moving machinery andagricultural tractors - stationary test condition
AS 2107-1987 Acoustics - Recommended design soundlevels and reverberation times for building interiors
AS 2221-1979 Acoustics - Methods for measurements ofairborne sound emitted by compressor units includingprimemovers and by pneumatic tools and machines
AS 2253-1979 Methods for field measurement of thereduction of airborne sound transmission in buildings
AS 2254-1988 Acoustics - Recommended noise levels forvarious areas of occupancy in vessels and offshoremobile platforms
AS 2399-1980 Acoustics - Personal noise dosemeters
AS 2436-1981 Guide to noise control on construction,maintenance and demolition sites
AS 2586-1983 Audiometers (IEC 645)
AS 2659-1988 Guide to the use of sound measuringequipment
AS 2900.7-1986 Quantities and units of acoustics
AS 2991-1987 Acoustics - Method for determination of
CORE 44
airborne noise emitted by household and similarelectrical appliances
AS 3534-1988 Acoustics - Methods for measurement ofairborne noise emitted by powered lawnmowers, edgeand brush cutters, and string trimmers
AS 3663-1989 Acoustics and mechanical vibration -Definitions of fundamental quantities and theirexpression as levels
AS 3713-1989 Acoustics - Industrial trucks - noisemeasurement
AS 3782-1990 Acoustics - Statistical methods fordetermining and verifying stated noise emission valuesof machinery and equipment
MODULE 1: 1
MODULE 1: CASE STUDIES
Noise manager
Chief executive officer
Production/engineering staff
Employee representatives
OHS committee
These case studies demonstrate:
• the practical nature of noise management;
• effective, low-cost noise control solutions;
• policies and organisational arrangements support-ing effective noise management programmes.
CASE STUDY 1: WARATAH WIRE PRODUCTS
CASE STUDY 2: JOHNSON AND JOHNSON
THIS MODULE
IS FOR THE
CONTENTS
PURPOSE
MODULE 1: 2
Waratah Wire Products (Sydney Wiremill) is asubsidiary of the Broken Hill Proprietary Company Ltd.and produces wire fencing products, barbed wire, nailsand steel reinforcing. The original factory was builtover 100 years ago, although a large proportion of theoperation has been modernised. The company hasapproximately 410 employees and is located in aresidential area of Sydney.
The noise reduction programme began after complaintswere received from nearby residents. Action was takento quieten the main offending sources. This was thebeginning of a noise reduction programme throughoutthe entire factory which has eventually benefited thework force and the company.
The main emphasis of the hearing conservationprogramme is on engineering noise control to bringnoise levels to below 90 dB(A). The driving force behindthis programme is an engineer who is specificallytrained in noise control. He has applied the basicprinciples of noise control to great effect and iscontinually trying new ways to further reduce the noiselevels in the factory.
The hearing conservation programme operates under abroad occupational health and safety policy whichprescribes that “managers and supervisors provideresources, systems, facilities, procedures and methodsof supervision to ensure the safety of employees”.
Employees receive information on all occupationalhealth and safety matters relevant to their particularjob at an induction training course held at thecommencement of their employment with thecompany. This includes advice on appropriate hearingprotection. Supervisors attend regular refresher safetycourses and are responsible for ensuring that hearingprotectors are worn by employees in designated areas.
BACKGROUND
THE HEARING
CONSERVATION
PROGRAMME
EMPLOYEE
TRAINING
CASE STUDY 1:WARATAH WIRE PRODUCTS
MODULE 1: 3
Pre-placement audiometry is performed by the residentoccupational health and safety nurse. Follow-up testsare made every two years. A computerised audiometricsystem, which provides reports for each of theemployees tested, has recently been purchased. Thesereports are stored at the health centre on the premises.
Noise contour maps of the entire factory have beendrawn. This has aided in the setting of priorities fornoise control. The daily noise doses of employees areassessed about every two years. Noise levels are alsomeasured when new equipment is purchased or existingmachinery is modified or relocated.
Numerous examples of engineering noise controlsolutions are to be found in the factory, and a selectionof these are described below. In most of the casesdescribed, hearing protectors were no longer requiredby the operators.
Wire is drawn to the required diameter on wire drawingmachines and then recoiled. There were fifteen of thesemachines producing noise levels of between 103 dB(A)and 105 dB(A) in the area.
The drawing mechanism required the use of a largemotor and a two-speed gear box. The original gear boxwas based on spur gears. After a few years, this gear boxbecame very noisy due to wear.
The manufacturer in England was asked for a quotationon a new gear box. The price was $6,000 and the noiselevel expected was 92 dB(A). The engineers then lookedat the possibility of using a helical gear box boughtlocally. The cost of these machines was alsounacceptable.
The gear box was eventually replaced by a belt drivewhich reduced the noise level considerably. Changingthe belt to change the speed was accomplished by usinga pneumatic lifter and a pivoting table to lift the motorand hence slacken the belts.
It was found that the maintenance-free life of the beltdrive was far longer than that of the gear box.
AUDIOMETRY
NOISE SURVEYS
EXAMPLES OF
ENGINEERING
NOISE
CONTROL
MODULE 1: 4
After experimenting with this one machine the samenoise control procedure was applied to all 15 machines.
SINGLE HOLE
WIRE DRAWING
MACHINES
Figure 1: Large wire drawing machine showing the pulleydrive system which replaced the two-speed gear box
.
Noise reduction: from 105 dB(A) to 85 dB(A)
Cost: $4,000 - $5,000 per machine
Many modifications have been made on these machinesin order to reduce the noise. These modificationsinclude:
• Filling the wire guide rings with sand to dampenthe impact vibration.
• Installing a pneumatic stopper for a swinging arm.This removed the impact noise which previouslyaccompanied movement of the arm.
• Placing old conveyor belt on parts of the guide trainwhere metal to metal contact was occurring.
• Supplying silencers with the pneumatic system toreduce the high-pitched sound of air release.
• Replacing spur gears with helical gears. Thisproduced a considerable noise reduction.
• Eliminating metal to metal impact of the wireretainer hitting the base by simply placing a pieceof rubber from an old flexible coupling under theretainer.
Noise reduction: from 98 dB(A) to 88 dB(A).
MODULE 1: 5
Several nail making machines were purchased eightyears ago. These machines produced noise levels up to104 dB(A). The solution was to build full enclosures.An additional safety benefit was that the enclosures alsoserved as guarding for the machines. When the door ofthe enclosure was opened, the machine automaticallyshut down. The enclosures were demountable whichmeant that maintenance could be easily carried outwithout the hindrance of the enclosure.
Noise levels were reduced to between 83 - 89 dB(A)depending on the measurement position. A great dealof noise was still escaping from the gap where the wireentered the enclosure so a small steel box wasconstructed around this inlet. The inside of the box waslined with 50 mm of sound absorbing foam. The foam
Figure 2: View of the nail making machine showing the totalenclosure.
Figure 3: Silencing box fitted to the enclosure.
NAIL MAKING
MACHINES
MODULE 1: 6
was covered with thin aluminium foil to prevent dustand grease accumulating. This treatment furtherreduced the noise level to 83 dB(A) from 89 dB(A) atthat position.
Noise reduction: from 104 dB(A) to 83 dB(A).
Nails were tumbled in a rotating drum called a“rumbler” for polishing to the finished product. Thisprocess was very noisy and was the dominant noisesource in an otherwise quiet part of the factory. Themain sources of noise were the gear drive mechanismand the impact of the nails on the walls of the drum.
Figure 4: Nail rumbler with sound damping material paintedonto the drum.
Noise control treatments consisted of:
• Painting sound damping material onto the outsideof the drum reducing the noise level by about 3dB(A);
• Overhauling the drive mechanism, replacingbearings and chains and replacing a steel gear witha nylon gear. The nylon gear was machined in thecompany’s own workshop.
GALVANISED NAIL
RUMBLERS
MODULE 1: 7
These treatments reduced the noise levels to an averageof about 85 dB(A) as shown in the following table.
Noise levels (dB(A)) at measuring positions
1 2 3 4
Before treatment 95-100 90-96 88-94 90-97
With damping 91-94 88-91 88-91 85-87
With overhaul of drive mechanism 87-92 85-89 83-87 82-84
Noise reduction: approximately 5 - 8 dB(A) dependingon measurement position.
The company required three nail polishing machines. Itwas decided to build these machines in its ownworkshops.
The steel nails are polished in a rumbler. Finished nailsare expelled from the machine via a chute and collectedin a tray at the bottom. Previous experience withsimilar noisy machines allowed the engineers toanticipate where the major sources of noise wouldoccur. Most noise would be produced by the impact ofnails on the drum and their impact on the expulsionchute.
The following engineering noise controls wereincorporated:
• The first step was to decrease the rotation speed ofthe drum to a point where the efficiency of theoperation was not compromised.
• The noise produced by the impact of the nails onthe chute was diminished by covering the chuteand the collecting tray with 1.6 mm rubber(Dunlop Flexide). This was in turn overlaid with asheet of special hard wearing nylon material (4.5mm Ralloy plastic).
• A piece of old conveyor belt rubber was used as abaffle in front of the chute to collect stray nails.
• Tico S, a cork based vibration damper, was usedunder the feet of the rumbler.
• A silencer was fitted to a fabric dust collector.These treatments were successful in reducing thenoise level to below 85 dB(A).
STEEL NAIL
RUMBLERS
MODULE 1: 8
Figure 5: Nail rumblers. The machines were designed andconstructed in-house with noise control treatmentsincorporated.
Figure 5 shows the rubber baffle and behind it the chutewhich was covered with rubber and hard wearing nylon.
Noise reduction: The noise level produced by themachines was 83 dB(A). It was estimated that withoutthe noise control treatments the noise level would havebeen between 89 and 92 dB(A).
Cost: (in 1983) Chute insulation: 4.5 mm Ralloy sheetplastic ( from Cadillac Plastics Australia bought insheets 2 m x 1 m - $126 per sheet). 1.6 mm rubbercanvas insertion (Dunlop Flexide) - $21 per metre.Silencer for dust collector, $250.
The original barbed wire making machines producednoise levels of 98 dB(A). The newer machines weresupplied with a complete enclosure and a slidingopening to allow full access to the working parts. Thenoise level was reduced to around 82 dB(A).
Figure 6: Barbed wire making machine with full enclosure.
BARBED WIRE
MAKING
MACHINE
MODULE 1: 9
Noise reduction: from 98 dB(A) to 82 dB(A).
Cost: The cost of enclosure was included in the totalprice of the machine as supplied by the manufacturer.
Figure 7: Furnace air fans showing intake silencer
Large fans supplied air to furnaces. The noise controltechniques included the installation of:
• anti-vibration mountings;
• silencers on air intake;
• rubber flexible connections;
• damping material on fan housing.
Noise reduction: 15 dB(A).
Several air compressors are in use. The oldest of thesehas been fitted with a silencer on the air intake, flexiblehose connections made from woven steel and neopreneanti-vibration mountings. These measures havebrought the noise level down to 91 dB(A). Newercompressors came supplied with complete enclosureswhich reduced the noise level to about 81 dB(A).Operating controls were located on the outside of theenclosure.
Noise reduction: (due to enclosure) 20 dB(A)
Cost: The enclosure was included in the total price assupplied.
AIR
COMPRESSORS
FURNACE
AIR FANS
MODULE 1: 10
CASE STUDY 2:JOHNSON AND JOHNSON
A very successful hearing conservation programme hasbeen carried out by Johnson & Johnson Pty Ltd (J&J).The company has reduced noise to a level at whichhearing protection is no longer necessary for themajority of the workforce. It has also eliminatedcompensation claims for hearing loss, and is very proudof its efforts.
J&J is an American multinational company whichproduces many familiar products such as Johnsons‚
Baby Powder, Shampoo, Carefree® Tampons, CottonBuds‚, cotton balls, and disposable plastic gloves. Thecompany employs about 1,000 people, most of whomhave non-English speaking backgrounds.
Although being described as a light industry, J&Jnevertheless used many noisy machines in itsproduction lines. These included carding machines,filling and packing machines, presses and fork lifttrucks. Before the hearing conservation programme,people working in these areas were receiving daily noiseexposure levels which exceeded 90 dB(A).
In the period 1981-83, a complete safety audit was madeon the company by a group under the acronymNATLSCO. This was a firm employed by the parentcompany in the United States of America to conductsafety audits on J&J companies around the world. Theinitial findings were disastrous and the commitment tohealth and safety of the parent company was so strongthat it recommended the division be closed down if itcould not lift its game!
With the necessary motivation behind them, thisAustralian subsidiary set about improving itsperformance in occupational health and safety.
The Training Section of J&J decided that to successfullytackle the problem the management had to beconvinced of the need for the programme. In 1984,educational materials were gathered from many
BACKGROUND
THE NOISE
MANAGEMENT
PROGRAMME
MODULE 1: 11
sources, but mostly from the suppliers of hearingprotectors and other noise control devices. With thisinformation, members of the Training Section produceda very comprehensive document on their hearingconservation programme. The hearing conservationprogramme gave guidelines on the following:
• company policy;
• the responsibilities of each department in regard tothe programme;
• relevant legislation;
• noise and the concept of daily noise dose;
• noise exposure guidelines, exposure limits (Leq(8h) =85 dB(A)), specifications for new plant, surveillanceguidelines;
• noise monitoring programme;
• noise control (guidelines for engineering controlsand personal hearing protection);
• audiometric testing programme (pre-employmentfor all employees and annually for those working innoisy areas);
• administrative responsibilities (consultation withemployees, employee training and notification oftest results, supervision and record keeping);
• in-house audit of the programme.
Training materials, including lecture notes, pamphlets,charts, videos, a model plastic ear and overheadtransparencies, were prepared. Training sessions on thenature and effects of noise, assessment of exposure andbasic noise control were held with both the supervisorgroup and the workers. Supervisors were issued with amanual on the hearing conservation programme andwritten safety objectives for their area of responsibility.
One particular technique was found to be successful inconvincing the supervisors and workers of theeffectiveness of hearing protectors. Sounds in the range90 dB(A) to 100 dB(A) were played through loud-speakers to the participants, who were then asked toplace earmuffs over their ears to notice the dramaticdrop in loudness.
The educational programme was a success in theopinion of the training personnel, however a degree of
MODULE 1: 12
enforcement was still necessary to ensure compliancewith rules for the wearing of hearing protection. It wasimportant that top management was committed to thesuccess of the programme.
The company encourages the workers to inform themanagement of any problems. Then the engineersmust act on the problem within a week.
A noise survey of the plant is carried out yearly by aconsultant to assess the daily noise doses of theemployees and assess the company’s progress in noisereduction.
Through the purchase of quiet machinery andengineering noise control on other equipment, thereliance upon personal hearing protectors was graduallymade unnecessary in most areas of the factory.
The company has included a buy quiet policy into itspurchasing guidelines for engineers. The stated policyis that a machine which exceeds 80 dB(A) at 1 metremust be fitted with noise-reducing panels. A majorpurchase of new machinery for the production ofshampoo saw the policy work well: the manufacturersupplied equipment within the specified limits.Machinery guards, made of perspex, also served aspartial noise enclosures.
Machinery manufacturers are not always able to complywith the 80 dB(A) limit, necessitating post-installationnoise control treatments. Details of such treatmentsare given below.
As supplied, machinery producing Cotton Buds‚®
produced noise levels of 92 dB(A). The manufacturerssuggested a complete enclosure. This option wasrejected because access was needed for maintenance andproduct adjustment. The solution was to only enclose
NOISE SURVEYS
NOISE CONTROL
BUY QUIET POLICY
EXAMPLES OF
ENGINEERING
NOISE
CONTROL
COTTON
BUDS®
MACHINES
MODULE 1: 13
the parts of the machine which produced noise. Thesepartial enclosures also served as safety guards andaccess to the internal parts was still possible throughinterlocked hatches which when opened, shut themachine down. All construction was done in-house.
Noise reduction: from 92 dB(A) to 84 dB(A).
Cost: $500 per machine.
Noisy parts of the machine were enclosed usingstainless steel and brushed aluminium. The inner wallsof the enclosure were lined with a special marine noisereducing material, FLS-20, obtained from a supplier ofacoustic materials. The material consisted of a layer ofloaded vinyl sandwiched between two layers ofpolyurethane foam. The foam was lined on the innersurface with thin aluminium foil to facilitate cleaningand prevent dust collecting on the foam. The foam wastreated for fire resistance.
Figure l: View of Cotton Buds® machine showing partialenclosures and ease of access.
The hopper/vibrator which supplied the plastic lids forthe Cotton Buds® containers was also a major source ofnoise. This source was greatly reduced by covering thehopper cover with a perspex lid lined with FLS-20.
MODULE 1: 14
Figure 2: The vibrator was covered with a perspex lid linedwith foam.
Noise reduction: from 88 dB(A) to 82 dB(A).
Cost: $400 per machine.
The newly purchased carding machines were suppliedby the manufacturer with full enclosures. The oldmachines were initially open and unguarded. Partialenclosures were constructed for these machines byJ&J’s own personnel.
Simple enclosures were constructed around the drivemechanisms of the machines. Enclosures consisted ofaluminium sheet with small perspex windows. Thesepartial enclosures served as safety guards as well asnoise insulators.
An important feature of the partial enclosures was theirease of removal for maintenance. To aid removal,wheels were fitted to each enclosure.
.
OLD CARDING
MACHINES
Figure 3: View of oldcarding machine withpartial enclosure alongsides. The enclosure isbuilt in sections and ison wheels for removalduring maintenance.
MODULE 1: 15
A machine which made disposable plastic glovesproduced noise levels up to 94 dB(A). Noise levels at theoperator’s position were reduced to 82 dB(A).
The glove making machine was to be relocated, sothought was given to reducing the operator’s noiseexposure and at the same time improve the efficiency ofthe process. The old machine was totally refurbished;the mechanical drive unit and all bearings werereplaced. A vibration packing unit was also replacedwith a quieter process. Metal to metal contacts wereeliminated where possible by using rubber inserts.
The waste plastic was drawn off through an exhaustduct. The fans which powered this Venturi system wereoriginally located just above the machine. This methodof waste removal was considered to be efficient, so itwas retained, but the fans were relocated to a nearbyplant room and silencers placed in the ducts.
Finally, the sides of the machine were enclosed usingsteel sheet with glass viewing panels. Reflected noisewas controlled by placing sound-absorbing panels abovethe machine. The whole machine was isolated in itsown room so that its noise would not intrude on otherquieter areas in the factory.
Figure 4: The glove making machine showing enclosed sides,the Venturi exhaust ducting above and the windows (in thebackground) of the enclosing room.
Noise reduction: from 94 dB(A) to 82 dB(A).
Cost: $7,000 (4 per cent of total machine replacementcost.)
PLASTIC GLOVE
MAKING
MACHINE
MODULE 1: 16
The machine which formed Carefree® Tampons fromcotton/rayon sliver produced a noise level of 88 dB(A) atthe operator’s position. A transparent enclosure(perspex, 6 mm), which included access doors, wasconstructed around the sides of the machine. Thisachieved a noise reduction of 5 dB(A) to 83 dB(A). Thenoise level at the operator’s position was slightly higher(85 dB(A)) because several of these machines wereoperating simultaneously in the room.
The noise control treatment was not fully efficientbecause noise still leaked from a few gaps between theperspex panels and out through the top, which was stillopen. The next step will be to seal the existing gaps,cover the top, and place sound-absorbing materialwithin the enclosure. These additional measures shouldfurther reduce the noise level by up to 10 dB(A).
As a safety feature, the machine guards were interlockedto automatically switch the machine off when anenclosure door was opened.
Noise reduction: from 88 dB(A) to 83 dB(A).
Noisy parts of the machine, mainly the drivemechanisms, were enclosed, reducing the noise levelfrom 86 dB(A) to 83 dB(A).
Noisy diesel fork lift trucks were replaced by quietelectric models.
Johnson & Johnson are justly proud of theirachievements in the control of noise. They have a buyquiet policy which seems to be working in most, but notall, cases. The need for personal hearing protectors hasalmost been eliminated and worker morale is high.
CAREFREE®
TAMPONS
MACHINE
CONCLUSION
FORK LIFT TRUCKS
COTTON BALL
MAKING MACHINE
MODULE 2: 1
MODULE 2: WALK-THROUGH AUDIT
Noise managerProduction/engineering staffMaintenance staffEmployee representativesOHS committee
A walk-through assessment can help to define the noiseproblem and provide the basis for a noise control plan.It is an informal audit of noise sources, possible noisecontrols and management measures to reduce noiseexposure.
The expected outcomes are that the noise managershould be able to:
• Identify problem noise areas/machines;
• Identify obvious noise control methods;
• Evaluate effects of major changes expected in theworkplace;
• Identify the need for a detailed noise control studyor design;
• Identify the need for revision of the personal hear-ing protection and education programme.
SETTING IT UP
ASSESSMENT PROCEDURE
THIS
MODULE
IS FOR
PURPOSE
OUTCOMES
CONTENTS
MODULE 2: 2
A WALK-THROUGH ASSESSMENT OFYOUR WORKPLACE
You may wish to arrange for the assessment to includethe entire workplace (if small) or only part of it. Choosean area that can be covered in about half a day.
It is crucial that you are accompanied by the rightpeople. You are likely to need people who understandthe work process and the machinery (engineering/production); operators of particular machines, healthand safety representatives or employee representatives;and people who control decision-making, planning andbudgets (management). Try and keep the group to aworkable size (say three to six people), since it may behard for larger groups to hold discussions in noisyareas!
If you have a sound level meter, it is useful to take thisalong to show the group indicative sound levels (if youare confident to do so). Measure noise levels at operatorear positions wherever possible. Pay particularattention to areas where operators use powered handtools such as pneumatic nut-runners and screwdrivers.Noise levels at operator ear positions in these situationsare usually much greater than those a few metres awayin the passageways and may surprise managers andengineers who believed there were no noise problems inthese areas.
Prior to embarking on your “walk”, assemble all therelevant information you can find relating to noise inthe area to be assessed. This may include:
• Previous noise survey reports;
• Manufacturers’ data on particular items of plant;
• Your own previous “walk-through” measurementsand observations;
• Previous comments by employees or others.
You may also find it useful to draw up an assessmentsheet for each small work area or machine, as a meansof logging the results /ideas /solutions /options putforward. Sample blank and completed noise assessmentreport forms are included at the end of this module.The forms follow the format of the four-step procedurefor a walk-through assessment, given below.
SETTING UP
MODULE 2: 3
The following four-step procedure is aimed atdeveloping an engineering noise control strategy. Eachstep is discussed in terms of the “sources”, “paths”, and“receivers” (employees). You should cover all four stepsfor each work area as a whole as well as for the primarynoise sources or machines in the area.
Sources
• What type of noise sources are evident?
- Mechanical sources: Impact? Out of balance?Transmission system (gears, chains, belts, etc.)?
- Hydraulic systems: Pump noise? Flow noise?Noise from moving load?
- Aerodynamic noise: Compressed air jet? Pneu-matic exhaust? Fan? Fan noise in duct?
- Thermodynamic noise: Noise from burners?
• Which of these noise sources or mechanismsappear to be most important?
Paths
• What type of noise paths are present?
- Mechanical coupling to a radiating surface? Struc-ture-borne?
- Airborne? Direct line of sight in a reverberantbuilding? Over a barrier?
- Duct-borne? Fan noise coming down a duct?
• Which paths are most important? (noise may bearriving at the receiver via several paths).
Receivers
• How many employees are affected? (See Module 5:Using Surveys).
• Where are they?
• Why are they there? Are they on any kind of jobrotation?
• What protection do they have? Are they wearing it?Is it appropriate? Do they know what noise levelthey are exposed to? When did they last have anoise education programme? (See Module 12:Personal Protection.)
ASSESSMENT
PROCEDURE
1. IDENTIFY THE
PROBLEMS
MODULE 2: 4
Example -John’s Story
As I walked towards the plant I could hear a distinctivetone. “You can’t do anything about those centrifuges”he said “they run at 15,000 rpm”.
Interesting, 15,000 revs per minute is 15,000/60 = 250revs per second. The source of the tone I could hearwas probably an imbalance in the centrifuge, causing atone at the frequency corresponding to the rotationalspeed. I already knew something useful before puttingmy foot in the door! I knew the type of source and thenoise-generating mechanism.
Up on the centrifuge floor, my suspicions about thequality of the installation were confirmed. The sixcentrifuges were bolted rigidly to the concrete floor andthe loud noise dominated everywhere. It was conductedinto the floor slab via the mountings and rigid pipeconnections (the path). It was conducted into the wallsand other panels via electrical cable trays and otherpipes. I asked myself why don’t people stop and thinkbefore doing this sort of installation?
The operators (the receivers) were on the centrifugefloor all day, either in the plant area, laboratory orlunchroom . All complained about the loud noise. Wasthe primary path into these rooms structural (throughthe slab) or air-borne (from the centrifugesthemselves)? I stood in one of the rooms with the doorclosed, then opened it. A bit more high frequency noisebut no difference to the tone. I could feel the floor,walls and windows vibrating and this tended to confirmthat the noise was structure-borne. With properisolation of the mountings and pipework, we should beable to improve this situation no end but we’ll leave thatto the experts. “You can’t do anything about thosecentrifuges”. Who says?
Sources
• Do we have to do it this way? Can we change theprocess and eliminate or minimise the source?
• Can we reduce forces? Impacts? Reduce air pres-sure? Speed?
• Is it a routine maintenance matter? (See Module 3:In-house Control).
2. IDENTIFY
OBVIOUS
TREATMENTS
MODULE 2: 5
• Can we isolate coupled components to reducetransmission of vibration to noise radiating sur-faces?
• Can we introduce vibration damping on surfaces toreduce their response to impacts?
• Are there mufflers/silencers readily available forthese aerodynamic sources?
Paths
• Can we increase the distance between source andreceiver?
• Can we introduce a localised cover or guard over anoise radiating surface or noise source?
• Is a simple enclosure of the source possible?
• Can we introduce simple screens or barriers be-tween sources and receivers?
• Can we simply introduce sound absorption in thespace?
Receivers
• Can some employees be located in booths or shel-ters?
• Can we easily change the layout to better separateemployees from machines?
• Is it possible to remove some employees to quieterareas?
• Can we make changes to routines to reduce em-ployees exposure time in the noisy area?
Before implementing extensive changes following theassessment above, you will need to consider whetherany major changes, likely to affect the work areas, areabout to occur. Consider changes to sources, paths andreceivers.
Sources
• Is this machine to be replaced soon?
• Is a new work process to be implemented? Newmachines added?
• Is the machinery to be upgraded or modified?
• Is a new plant to be built?
3. EVALUATE
EFFECTS OF
MAJOR CHANGES
EXPECTED
MODULE 2: 6
• Is there a purchase policy or noise specification forthe new plant/machine? (See Module 8: BuyQuiet).
Paths
• Is the layout of the work area to be altered?
• Are architectural changes planned? Partitions?
• Are you moving to new premises?
Receivers
• Are personnel to be moved?
• Are the above changes in sources and paths likely toresult in relocation of employees?
• Will retraining be needed (thus providing an oppor-tunity for a noise education program)?
You can use these changes as an opportunity tointegrate aspects of your noise control plan into youroverall workplace planning. This may mean bringingsome changes forward for noise control reasons, ordeferring some treatments identified in Step 2. Youraims must be to ensure that the changes result in aquieter workplace and that this occurs within areasonable time frame.
Example - Plastics Recycling Company
A plastics recycling company had three granulatorswhich generated noise levels typically 95-110 dB(A) atthe operator’s position, while grinding. The companyidentified a low-cost treatment in the form of anabsorptive lining in the feed chute (operator’s position)and acoustic shrouding around the discharge point.
At the same time, however, it was apparent that theoldest (and noisiest) of the granulators was almost duefor replacement. Information from an Australianmanufacturer of plastics granulators indicated that anew granulator would emit a noise level of about 85dB(A) at the operator’s position while grinding, that is,some 25 dB(A) quieter than the old unit!
Accordingly the new unit was budgeted for, and theother two units were earmarked for later replacement.As a result of the time lag in obtaining budget approvaland completing purchase and commissioning of thenew machine, it was decided that the old machine
MODULE 2: 7
(along with the other two machines) should be providedwith the low-cost treatment. This reduced noise levelsto about 100 dB(A) on the oldest machine and about 90dB(A) on the other two.
A walk-through assessment will highlight lots of areaswhere reductions in noise can be achieved with minimalor moderate expenditure. However, you are also likelyto find machines, or even whole work areas where thereduction of noise is likely to involve considerableexpenditure and technical complexity. Beforeembarking on such a costly exercise, it may be wise toseek the assistance of an acoustical consultant. Thisperson can introduce the expertise needed to identifythe options for noise control, evaluate costs andbenefits, and carry out detailed design work. Acontractor would then be engaged to carry out thework. Module 4: Consultants deals with the roles ofconsultants and contractors and how to brief them.
You may require external expertise if, when faced withthe following questions, you cannot answer them:
• We feel it best to enclose this machine, but how dowe do it in the most cost-effective way, still allowingfor cooling and access? Would it be better toreconsider treating the source?
• How do we design the new control room so that itis effectively isolated from the surrounding noiseand vibration?
• How do we design the new plant to minimise noise?
• We have a fixed budget for noise control work.How do we best spend it?
• Is it more cost-effective to enclose this machine(with still the noise of other machines) or to applyabsorptive material to the work area to achieve anoverall reduction in noise level?
• If we treat the airborne noise path, will the struc-ture-borne noise path still be significant? How dowe then treat the structure-borne path?
4. IDENTIFY THE
NEED FOR
DETAILED
CONTROL STUDY
OR DESIGN
MODULE 2: 8
Work Area: Sheet: of Date:
Location: Assessment Team:
Machines: Background Data:
SOURCES:
Mechanical: • Impact
• Vibration
• Rotation
Aerodynamic: • Pneumatic
• Fan
Turbulent flow: • Duct
• Pipe
Other:
PATHS:
Airborne: • Open air
• Reverberantspace
• Barrier
Structure-borne: • Building
• Coupling tosurface
Duct-borne:
Other:
RECEIVERS:
No. affected: • Operator
• Bystander
• Other
Location: • Operator
• Bystander
• Other
HPD Worn: • Operator
• Bystander
• Other
Other Comments:
Task/Item Identify Obvious Major DetailedProblem Treatment Changes Study
Noise Assessment Report Form
MODULE 2: 9
Work Area: Sheet: of Date:
Location: Assessment Team:
Machines: Background Data:
SOURCES:
Mechanical: • Impact
• Vibration
• Rotation
Aerodynamic: • Pneumatic
• Fan
Turbulent flow: • Duct
• Pipe
Other:
PATHS:
Airborne: • Open air
• Reverberantspace
• Barrier
Structure-borne: • Building
• Coupling tosurface
Duct-borne:
Other:
RECEIVERS:
No. affected: • Operator
• Bystander
• Other
Location: • Operator
• Bystander
• Other
HPD Worn: • Operator
• Bystander
• Other
Other Comments:
Task/Item Identify Obvious Major DetailedProblem Treatment Changes Study
Noise Assessment Report Form
StudyStudyStudyStudyStudyneeded to:needed to:needed to:needed to:needed to:1. Assess1. Assess1. Assess1. Assess1. Assesswhetherwhetherwhetherwhetherwhethervibration/vibration/vibration/vibration/vibration/noise can benoise can benoise can benoise can benoise can bereduced atreduced atreduced atreduced atreduced atsourcesourcesourcesourcesource
2. Assess2. Assess2. Assess2. Assess2. Assessvibrationvibrationvibrationvibrationvibrationisolationisolationisolationisolationisolationfrom floorfrom floorfrom floorfrom floorfrom floorbybybybybyremountingremountingremountingremountingremounting
RankingRankingRankingRankingRanking
floor, pipes 2floor, pipes 2floor, pipes 2floor, pipes 2floor, pipes 2
1500 rpm 11500 rpm 11500 rpm 11500 rpm 11500 rpm 1
Drive belt whistleDrive belt whistleDrive belt whistleDrive belt whistleDrive belt whistle
----------
----------
--------------------
✓
✓
✓
✓
✓
11111
Walls to lab 3Walls to lab 3Walls to lab 3Walls to lab 3Walls to lab 3
Floor 2Floor 2Floor 2Floor 2Floor 2
---------------
33333
---------------
1 (Foreman)1 (Foreman)1 (Foreman)1 (Foreman)1 (Foreman)
Lab, control rm,Lab, control rm,Lab, control rm,Lab, control rm,Lab, control rm,lunch rm, plantlunch rm, plantlunch rm, plantlunch rm, plantlunch rm, plant
---------------
----------
22222
----------
----------
Noise highlyNoise highlyNoise highlyNoise highlyNoise highlytonaltonaltonaltonaltonal
• Move lunch• Move lunch• Move lunch• Move lunch• Move lunchroom to quietroom to quietroom to quietroom to quietroom to quiet
areaareaareaareaarea
---------------
ActionActionActionActionAction DateDateDateDateDate
1. Foreman1. Foreman1. Foreman1. Foreman1. Foremanarrangearrangearrangearrangearrangeserviceserviceserviceserviceservice
10/310/310/310/310/3
2. Noise2. Noise2. Noise2. Noise2. Noisemanager speakmanager speakmanager speakmanager speakmanager speakto a consultantto a consultantto a consultantto a consultantto a consultant
24/224/224/224/224/2
CentrifugesCentrifugesCentrifugesCentrifugesCentrifugesnot due fornot due fornot due fornot due fornot due forreplacementreplacementreplacementreplacementreplacementfor at least 5for at least 5for at least 5for at least 5for at least 5yearsyearsyearsyearsyears
DisconnectDisconnectDisconnectDisconnectDisconnectpipes frompipes frompipes frompipes frompipes fromslabslabslabslabslab• Service to• Service to• Service to• Service to• Service tocure imbalancecure imbalancecure imbalancecure imbalancecure imbalance• Block gap• Block gap• Block gap• Block gap• Block gapround beltround beltround beltround beltround beltcovercovercovercovercover
IsolateIsolateIsolateIsolateIsolatecentrifugecentrifugecentrifugecentrifugecentrifugefrom floorfrom floorfrom floorfrom floorfrom floor
9/2/959/2/959/2/959/2/959/2/95
Manager, foreman, noise managerManager, foreman, noise managerManager, foreman, noise managerManager, foreman, noise managerManager, foreman, noise manager
90 dB)A) plant.90 dB)A) plant.90 dB)A) plant.90 dB)A) plant.90 dB)A) plant.75dB(A) Office Tonal noise75dB(A) Office Tonal noise75dB(A) Office Tonal noise75dB(A) Office Tonal noise75dB(A) Office Tonal noise
Main plant, 1st floorMain plant, 1st floorMain plant, 1st floorMain plant, 1st floorMain plant, 1st floor
6x centrifuge (Model z,y.z)6x centrifuge (Model z,y.z)6x centrifuge (Model z,y.z)6x centrifuge (Model z,y.z)6x centrifuge (Model z,y.z)
Veg oil process areaVeg oil process areaVeg oil process areaVeg oil process areaVeg oil process area 4 74 74 74 74 7
---------------
MODULE 3: 1
MODULE 3: IN-HOUSE CONTROL
Noise managerProduction/engineering staff.
One of the best ways of reducing workplace noise “at thesource” is via a program which ensures that noise isconsidered as part of the maintenance, modification andupgrading of the plant. This module sets out a“practical diagnosis” procedure which can be carriedout by maintenance personnel to tackle noise problems.This module follows on from Module 2: Walk-ThroughAudit in which the main noise sources, paths andreceivers were identified.
By using this module, you should be able to:
• conduct a “practical diagnosis” on each machine ofinterest;
• develop a maintenance program to minimise noisefrom existing plant, including specific noise controlitems which need maintenance;
• identify and set priorities for modifications to theplant to reduce noise, for integration into thecompany noise control plan;
• establish a process for considering noise in minorplant upgrades;
• minimise noise from maintenance work itself.
WHAT YOU WILL NEEDOVERVIEW OF MAINTENANCE AND MODIFICATIONPRACTICAL DIAGNOSISDIAGNOSTIC TESTSMAINTENANCE OR MODIFICATION?UPGRADING THE PLANTMINIMISING MAINTENANCE NOISECONCLUSIONREFERENCED DOCUMENTSAPPENDIX
THIS MODULE
IS FOR
PURPOSE
OUTCOMES
CONTENTS
MODULE 3: 2
REDUCING NOISE THROUGH “IN-HOUSE” MAINTENANCE, MODIFICATION
AND UPGRADING OF PLANT
To use this module, you will need the results of previouswalk-through assessments (see Module 2: Walk-through Audit) and any previous noise survey reports.You may wish to obtain a copy of the references listed atthe end of this module.
The result of the initial walk-through assessmentsshould have highlighted:
• machines requiring basic maintenance or modifica-tion (involving you and your staff);
• areas or machines requiring a noise control studyusing an external consultant;
• any changes about to take place which may replacethe need for either of the above;
• any broad options available for noise control.
The figure below presents an overview of the proceduresinvolved in maintenance and modification of existingplant to minimise noise.
WALK-THROUGH ASSESSMENT
SOURCES
PATHS
RECEIVERS
PRACTICAL DIAGNOSIS
PROBLEM IDENTIFIED
MODIFICATION
SOLUTION OBVIOUS?
YES
NO
PRIORITISE AND CARRY OUT WORK
EVALUATE OTHER
OPTIONS
SEEK ADVICE FROM
CONSULTANT
NO
SEEK ADVICE FROM CONSULTANT
YES
MAINTENANCE OR MODIFICATION NEEDED?
MAINTENANCE
CARRY OUT MAINTENANCE
PLACE ITEM ON MAINTENANCE
SCHEDULE
CONDITION MONITORING
PROGRAM NEEDED?
OVERVIEW OF
MAINTENANCE
AND
MODIFICATION
WHAT YOU
WILL NEED
MODULE 3: 3
This section presents a series of diagnostic steps whichcan be carried out by an engineer or maintenancesupervisor with a thorough understanding of themachines and a basic knowledge of noise. No soundmeasuring instruments are needed for this procedure,which is based on the work of S A Worley(1), at LucasDiesel Systems, London. In cases which are beyond thescope of this procedure, the assistance of a consultantwith sophisticated measurement and analysisequipment may be needed.
The procedure, summarised in Table 1, consists of astructured series of listening tests based on fourquestions:
Q1. What kind of noise is this machine producing?
Q2. What is it in this machine which might becausing this noise?
Q3. What tests can I do to eliminate some of thepossibilities?
Q4. What are the answers and solutions I am lookingfor?
Even if you had started to answer some of thesequestions in your initial “walk-through” assessment, itis advisable to start from Q1 and work through to Q4with each machine.
The work you do now will not be wasted even if aconsultant is eventually called in, since your knowledgewill save the consultant time and the company money.
Table 1 on the following pages lists a series of testswhich should be followed systematically duringpractical diagnosis. Each test is designed to identify aparticular noise generating mechanism. The tests aredescribed in detail on pages 5 to 8. They should only becarried out by competent staff and where tests can bedone safely.
PRACTICAL
DIAGNOSIS
DIAGNOSTIC
TESTS
MODULE 3: 4
Table 1: Practical Diagnosis Procedure
Follow Q1 down until you find the right description then moveto Q2 and so on:
Ql Q2 Q3 Q4Type of noise Possible causes Tests Examples of Treatments
1. VARIES WITH TIME Reduce impact velocity and rateImpact of change of working forces (e.g.(e.g. thump, Impact of shear on press tool, soft face onbang, crash) machine parts hammer). Cushion impact with
• guards 1,2 resilient material. Buffer at end• working forces 1,3 of actuation travel. Damp• clutch 1,2,3 resonant response of structure• indexing 1,3 with self-adhesive damping• punch break sheet. Reduce backlash in -through 1,3 drives, mass of moving• other parts.
Component or scrap Reduce drop height, cushionhandling impact as above, damp resonant• chute 1,3 response as above, fit stock tube• bin 1,2,3 liner, reduce mass of moving• scrap on scrap 1,3 parts.• other
Cyclic Load-related Reduce noise of sources related(e.g. varying • louder on load 2,6,14 to load condition. Reduce noiserepeatably with • louder off load 2,6,14 of sources which are independ-each cycle of a ent of load.process)
Hydraulics Check control system to ensure• pipework 5,6 not pumping into closed• pump 5,6 volume. Fit hydraulic silencer• valves 5,6 or accumulator if strong• other pressure fluctuations in fluid.
Isolate valves, pipes and loadfrom structure.
2. FREQUENCY CHARACTERTonal Mechanical Replace toothed belts, with
transmission V-belts, if synchronisation not• toothed belt vital, otherwise with half- drives 6.9 cylinder tooth profile. Replace• slipping flat belts 6.9 belt tensioning mechanism,• slipping V-belt 6.9 replace worn, stretched belts.• flapping drive belt 6.9 Replace worn gears with nylon• gear box 6,7,9 gears, if possible check shafts for• worn bearings 8 bending. Check gear box oil• other level and thicken if needed.
Replace worn bearings.
Cutting action Ensure correct tool clamping,• tool chatter 2,5,10 geometry, position and sharp• saw blade 2,10 ness. Ensure workpiece is• workpiece 3,5 adequately clamped with vibration damping on vibrating surfaces.• solid obstruction 9 Ensure sawblades are sharp. Use near rotating damping collars and plugs in cutter expansion slots. Remove or• tool vibration 10 provide air relief in solid• vibration in obstructions near rotating machine frame 5,11 cutters.• other Isolate machine frame.
MODULE 3: 5
Hydraulics As above, plus use quieter• pump or 5,6 pump, fit flexible pipe to pump support inlet and outlet and smooth entry• pipework 5,6 and exit. Ensure pump supply pipe• valve 5.6 is large enough in diameter so that• load 5,6,14 pump fills correctly and no air• other leaks on pump inlet.
Air flow Check fan for build-up of dirt,• fan noise 2,5,12 defects in impeller blades,• whistling air 13 imbalance, obstructions, abrupt• other bends or changes of section,
missing silencers. Check if fanduty is appropriate. Isolate direct-drive motors from frame. Checkfor rattling or whistling dampers,valves or grilles.
Distinctive Compressed air Reduce air pressure, fix leaks, usenon-tonal exhaust proprietary quiet nozzle or quietnoise (e.g. • component hand-held blow gun, preferablyreciprocating ejection 1,2 with regulator. Fit porouscompressor, • swarf removal 1,2 pneumatic exhaust silencers to allair jet, • component 1,2 ports, using a long pipe if rapidgears) drying release needed. Use fluid wash for
• air powered 2 swarf removal, and chemical orthermal method for drying.
Reciprocating Fit proprietary intake silencers,compressor check valve seating plate, reduce• intake 2,5 piston slap with crankcase oil• valve seating 2,5 additive. Relocate to remote area,• piston slap 2,5 or replace with new silenced unit.• other
Ql Q2 Q3 Q4Type of noise Possible causes Tests Examples of Treatments
TEST 1 Location of sources of impacts
Listen to the machine and identify the events whichoccur or the parts of the machine (or components)which make contact, running the machine at reducedspeed if possible, or running automatic machines undermanual control.
TEST 2 Isolation of suspected noise sources
Operate parts of a machine which are suspected noisesources in isolation. If this is not possible, disablesuspected parts and operate the remainder. Disablingthe most significant source will cause the greatest noisereduction.
TEST 3 Identification of resonant structures and panels
Excite the parts which are suspected to resonate (ring)in response to impacts, by striking each in turn with a
MODULE 3: 6
ball-peen hammer. Compare the tones generated tothose heard when the machine is running. Ringing ofthin panels can sometimes be identified by applyinglight manual pressure. Resonance can sometimes beidentified by changing the forcing frequency (by chang-ing the drive speed) in which case there will be a sud-den drop in noise level when the drive speed changesaway from the panel resonant frequency.
TEST 4 Sources with unusual time variations
Look for a source of noise generation which undergoeschange while conditions elsewhere remain the same(for example, the rattle of bar stock on an automaticlathe may change as bar length changes).
TEST 5 Location of radiating surfaces
The loudest sound radiation is usually located near thepoint of highest sound level around the machine(though if distant from the operator it may not besignificant). You may be able to temporarily suppressthis radiation by covering it with a limp heavy loadedvinyl sheet to assess the difference. Feeling vibratingsurfaces by hand does not give a good indication. It isbetter to use a stethoscope or place the ear close to asurface (where safe to do so).
TEST 6 Characteristic sources within a machine
The covers may be removed, one at a time, (taking allsafety precautions) to reveal sources within the ma-chine. Look for sources with noticeable characteristics.
TEST 7 Location of transmission eccentricities
Noise which is modulated (that is has a noticeable rapidfluctuation in level, for example, throbbing) is oftencaused by bent shafts or eccentrically mounted gearsand pulleys. The rate at which the noise fluctuates isdetermined by the rotational speed of the defectivecomponent. Change the speed of each inspected itemand listen for a change in modulation, or try and countthe number of modulations per minute and relate thisto components which run at that speed.
MODULE 3: 7
TEST 8 Location of worn bearings
If the noise level increases markedly as the rotationalspeed of the shaft is increased, then it may be due toworn bearings. Noise will be radiated from the bearingcasing and may be detected by measuring excessiveshaft run-out.
TEST 9 Location of sources of tones
Change the speed of the different machine componentsin turn and note which change most affects the leveland frequency of this tone.
TEST 10 Test of tool or sawblade errors
Check the quality of the machined surface or cut toindicate tool chatter, clamping or positioning problemsand blade or tool wear.
TEST 11 Location of loose panels or components
Look for rattles, checking these by hand in lightstructures (where safe) or by restraining with clampsor stops in larger structures (in which case thestrength and stiffness must match that of the struc-ture).
TEST 12 Test for fan noise
Switch off each fan in turn to identify any noisy units.Excessive low frequency noise may be due to a fanimbalance or running near stall condition, while atonal noise may indicate an obstruction, a blade defect,poor mounting or running at higher than rated speed.
TEST 13 Test for flow-generated noise
Remove in turn all sharp edges and constrictions fromthe flow.
TEST 14 Effect of load on system
Compare the noise level at idle with that when underload. Identify noise-generating mechanisms which areonly active, or which change, under load. If noisierwhen under load, these mechanisms dominate. If
MODULE 3: 8
noise is the same or less under load, look at the mecha-nisms which do not change with load.
There are many other tests which you can develop foryour workplace. It is good practice to document theseand put them into a checklist or questionnaire formatfor others to use.
The treatments listed in Table 1 are only a sample of themany techniques available. A good practical reference isNoise Control - Principles and Practice (2). There arealso courses run in most Australian States and Territo-ries on engineering noise control.
Having undertaken the “practical diagnosis” step, youwill have identified a number of problems and solutions,some of which you will have acted on immediately.Many solutions, however, will need to be scheduled forfuture implementation.
For the noise control plan, you need to advisemanagement on what needs to be done, what can beachieved in-house and with external assistance andwhat resources will be required.
The treatments you need to carry out as a result of yourpractical diagnosis fall into two categories:
• maintenance (repairing/refurbishing an item to itsproper state);
• modification (modifying or adding to the machinefor the specific purpose of reducing noise).
Develop a program for maintenance which anticipatesnoise problems occurring and which enables noiseproblems to be picked up during routine work, as wellas addressing the existing problems above. Whenexamining any noisy machine the first question toresolve is “Was this machine quieter in the past?” If so,what has changed: is it the job or process, the material,the tooling, the machine operating conditions, or is theextra noise due to wear and tear in the machine?
In the case of expensive or critical items of plant, youshould consider introducing a “machine condition
MAINTENANCE
OR
MODIFICATION
MAINTENANCE
MODULE 3: 9
monitoring” procedure. This is based on themonitoring of vibration levels on the machine andcomparison with baseline vibration levels to followtrends which may lead to failure of the machine. Thereare a number of reasonably priced measuring systemsavailable to achieve this. While noise and vibration arepowerful tools for predictive maintenance, Norton (3)
highlights several questions which need to be askedwhen costs and benefits are considered:
• Do noise and vibration measurements suit theparticular maintenance system and the machinesbeing used?
• What instrumentation is needed to provide themost economical system?
• Are specialised personnel essential or can personnelalready available perform this task?
• Can the use of noise and vibration measurementsreduce operation or maintenance costs to give animprovement in plant economy?
Other considerations include whether an intermittent(manual) system is sufficient or a permanent system isneeded, what measuring points to use, and how theinformation is to be analysed and used. Norton (3) givesa good overview of this topic and illustrates some of thefaults which can be detected by this procedure (seeAppendix to this module).
NOTE Your maintenance program should alsoinclude existing noise control equipment.For example, check for poor sealing ofenclosure doors, degradation of acousticlinings, clogging of silencer lining perfora-tions, missing silencers, vibration isolatorswhich have “bottomed” and degradation ofimpact-absorbing surfaces.
The solutions or treatments which you identify asmodifications to the machinery need to he prioritisedand programmed in your work program as well aswithin the company’s noise control plan.
MODIFICATION
MODULE 3: 10
Where there is more than one possible solution, youmay need to do a cost/benefit analysis of the options incooperation with the noise manager (see Module 9:Evaluating Options).
Where there is significant expenditure involved and youfeel the problem is beyond your level of expertise,recommend that a consultant be called in for furtherevaluation or confirmation.
We have looked at practical diagnosis on existing plant,and you have developed a maintenance andmodification program. But what about the situationwhere you are asked to upgrade the plant in someminor way ( for example, fit an air nozzle to clean dustoff a conveyor, install a ventilation fan or design acomponent collection system)?
These minor additions can easily add significantly to thenoise in the workplace unless proper measures aretaken in their design and installation.
Firstly, you need to be aware of the company’s noiseexposure goal for the area, so your upgrade will notequal or exceed this level, making it difficult tomaintain the goal in future upgrades.
The following process is suggested:
• Consider what the upgrade needs to achieve, andwhat is the quietest, effective way of doing so. Aprocess which produces lots of noise is unlikely tobe cost-efficient anyway.
• Select quiet components. These may or may not becovered by your buy quiet policy (see Module 8:Buy Quiet).
• Design for minimum impacts or vibrating forces.
• Isolate impacting or vibrating parts from thesurrounding structure. NOTE: A common mistakeis to install an isolating layer then proceed to boltdirectly through it, thus short circuiting the isola-tor! Isolating grommets are available for thispurpose.
• Consider future maintenance needs. Training ofmaintenance staff is important if this process is tobe carried through.
UPGRADING
THE PLANT
MODULE 3: 11
Maintenance work can itself be very noisy and theemployees in your section need to gain the benefits ofan effective noise control program.
This means looking for the quietest way to do the jobeffectively, whether in the workshop or on site. Theprinciples established in your practical diagnosisprocedure should be a useful guide in minimising noiseof your own operations.
Here are a few additional pointers:
• Use quiet air nozzles, for example, for cleaning.
• Use “dead-blow” hammers where possible instead ofhard hammers.
• Avoid dropping tools or machine parts onto hardsurfaces (use a mat).
• Use pressure rather than impact to move or shapemetal where possible.
• Use limp damping mats when working on resonantsurfaces or panels.
The use of personal hearing protection will be essentialin many instances and your management of this isimportant. The staff need to know in what areas of theplant they will need personal hearing protection, andhow to fit and maintain their protectors. The noisemanager can assist with this.
Two elements are crucial to your success with thismodule:
• Your own level of commitment to reduction ofnoise in the workplace;
• The training of your staff in specific aspects of noisecontrol.
The noise reductions you do achieve are likely to be themost cost-effective your company will manage.
MINIMISING
MAINTENANCE
NOISE
CONCLUSION
MODULE 3: 12
1. Worley, S. A. A Practical Diagnostic ProcedureLeading to Noise Control by Engineering Means.Institute of Mechanical Engineers PublicationC406/016, London, 1990.
2. Bruel and Kjaer. Noise Control - Principles andPractice. Bruel and Kjaer Pty Ltd, Denmark, 1986,available from David Reid Technology Ltd, PO Box1898, Auckland.
3. Norton, M.P. Fundamentals of Noise and Vibra-tion Analysis for Engineers. Cambridge UniversityPress, Cambridge, 1989.
The SHARE registry may be able to help you find anexisting solution used by another company with asimilar problem. SHARE (Safety and HealthAccumulated Research Experience) aims to identifysuccessful solutions to common health and safetyproblems and promote widespread application of thesesolutions in workplaces.
Copies of SHARE solutions on noise are available from:
Occupational Safety & Health Victorian Department ofService LabourGeneral Manager’s Office Public Relations and
Information Branch62 The Terrace Level 22, Nauru HousePO Box 3705 80 Collins StreetWELLINGTON 6001 MELBOURNENew Zealand Victoria 3000
AustraliaTelephone (04) 471 2937 Telephone (61 3) 655 6332
REFERENCED
DOCUMENTS
ADDITIONAL
RESOURCE
MODULE 3: 13
APPENDIX
Some typical faults and defects that can be detectedwith noise and vibration analysis (Norton(3))
Item Fault
Gears Tooth meshing faultsMisalignmentCracked and/or worn teethEccentric gears
Rotors and shafts UnbalanceBent shaftsMisalignmentEccentric journalsLoose componentsRubsCritical speedsCracked shaftsBlade lossBlade resonance
Rolling element bearings Pitting of race and ball/rollerSpallingOther rolling element defects
Journal bearings Oil whirlOval or barrelled journalJournal/bearing rub
Flexible couplings MisalignmentUnbalance
Electrical machines Unbalanced magnetic pullsBroken/damaged rotor barsAir gap geometry variations
Miscellaneous Structural and foundation faultsStructural resonancesPiping resonancesVortex shedding
MODULE 4: 1
MODULE 4: CONSULTANTS
Noise managerProduction/engineering staff.
When using external noise and vibration consultantsand contractors, you need some idea of their roles andlimitations in order to make the best use of theirservices.
With the help of this module you should be able to:
• identify and define the project which the consultantor contractor is to undertake;
• select a consultant or contractor capable of provid-ing the services you need;
• brief the consultant or contractor on what isneeded and what services they will provide;
• liaise with or supervise them during the work.
CONSULTANT OR CONTRACTOR?
USING A CONSULTANT OR CONTRACTOR
SUMMARY
THIS MODULE
IS FOR
PURPOSE
OUTCOMES
CONTENTS
MODULE 4: 2
GETTING THE BEST FROM CONSULTANTSAND CONTRACTORS
A consultant may provide a range of services including:
• conducting a noise survey;
• noise training;
• noise control (measurements analysis and design);
• legal technical services;
• liaising with statutory authorities.
The rationale for calling in a consultant is that byretaining the services of an independent expert, theorganisation can identify the most cost-effective noisecontrol solutions while satisfying statutory and othertechnical requirements. When used effectively,consultants can save the organisation their fees manytimes over.
A consultant however, is only a provider of expertise,and does not install any noise reduction treatments.This is the task of the contractor. A contractor isneeded when your own tradespeople don’t have the timeor the required detailed knowledge of the properties ofmaterials and proper installation methods.
You can, in some cases, go directly to a contractorwithout involving a consultant, that is, if the job issimple and straightforward, if the cost to theorganisation is not high or if you have sufficient in-house expertise to be sure you have the best option. Insuch cases, contractors usually have effective off-the-shelf solutions which they can offer at reasonable cost(for example, absorptive linings for vehicle cabs andmodular enclosure systems).
Where there is significant cost involved (say more than$10,000), technical complexity, a legal requirement or arange of options to be evaluated, it is likely to bebeneficial to use a consultant.
CONSULTANT
OR
CONTRACTOR?
MODULE 4: 3
The following table summarises the roles andlimitations of consultants and contractors.
Consultant Contractor
Provider of expertise Provider of skill
Able to carry out detailed Carries out only very limitedacoustic/vibration measurements noise or vibration measurementfor identifying noise sources
Analyses noise sources to Limited noise analysis onlydetermine ranking in order ofnoise emission and likely overallnoise reduction if given sourcesare treated
Can provide detailed analysis of Can provide detailed analysisbenefits of noise control options of costs of some noise
control options
Can specify noise control Can specify noise controltreatments in detail, not specific treatments in detail,to a proprietary brand normally specific to their
own product or service
May sometimes provide working Normally provides workingdrawings drawings
May arrange quotes from a Provides quotes for specifiedrange of contractors work and may arrange for a
consultant to be called in ifneeded
Does not carry out the Carries out the installation workinstallation work
May provide site or workshop May be supervised directly bysupervision of contractor clientMay conduct verification tests May conduct verification tests(that is, that specified noise levelsare achieved)
ROLES AND
LIMITATIONS
A paint manufacturer had an area where the noiseappeared to be dominated by a large ball mill, thoughthere was ancillary plant also generating noise. Thecompany called in a consultant to assist with the designof an enclosure. The company’s concept was of a largestructure enclosing the whole mill, including the drive,with an opening in the roof for cooling and a series ofbaffles to reduce noise through the roof. Theconsultant immediately recommended against thisapproach, since to open the roof would aggravate anexisting neighbourhood noise problem. The companystressed that the enclosure must not cause the mill tooverheat as this may affect the product
The consultant’s first task was to verify that treatmentof the mill was in fact the best option. What residualnoise would the ancillary plant cause? What if the millwere to be enclosed, but not the mill drive? Varioustests were conducted to show that the noise of the
EXAMPLE: PAINT
MANUFACTURER
MODULE 4: 4
ancillary plant and mill drive were well below that of themill.
The consultant was then able to design a temperature-controlled enclosure which excluded the drive motor,but provided a reduction of about 17 dB(A) in millnoise. The overall noise reduction was about 10dBA andthe cost was much less than that of the company’senclosure concept.
The following four-stage process emphasises the use of aconsultant or contractor for engineering noise controlwork. However, it may also apply to other noisemanagement tasks or even non-noise work, for whichexternal assistance is required.
To identify and define the project which the consultantor contractor is to undertake, you should first haveconducted a noise audit of the workplace (see Module 2:Walk-through Audit), or have had a noise survey done(see Module 5: Using Surveys). These steps will provideinformation on which work areas or machines requirepriority treatment.
Decisions need to be made concerning:
• the work area(s) or machine(s) which need noisecontrol work;
• the desired final noise level, for example:
- noise reduced to a specified policy limit;
- noise reduced “as far as workable”;
- noise reduced to comply with the statutory limitor a notice;
• any technical or operational constraints, for exam-ple:
- minimal restriction on production during noisecontrol work and none after this;
- minimal restriction on maintenance access;
- general safety requirements;
- any airflow, thermal or other technical require-ments;
• budgetary constraints.
USING A
CONSULTANT
OR
CONTRACTOR
1. IDENTIFY
AND DEFINE
THE PROJECT
MODULE 4: 5
These points need not be “set in concrete”, but at leastform a basis for your initial discussions with theconsultant or contractor. Ultimately, they may formpart of the brief for the contract.
Acoustical consultants and contractors are listed under“Acoustic Consultants” in the Yellow Pages (seeAppendix 3 in Core). The information contained theremay help you establish a short list. The followinginformation may assist you in your choice.
Qualifications/Affiliations
Consultants should have an engineering or relatedtertiary qualification and/or be members of theAustralian Acoustical Society, the Association ofAcoustical Consultants Australia, the Association ofConsulting Engineers Australia or equivalent NewZealand qualifications. Contractors may or may nothave tertiary qualifications, but should be affiliated withtrade or industry organisations which impose a code ofethics. In Victoria, Australia there is an Association ofNoise Control Engineering (contactable via PO Box 14,Moorabbin, Victoria 3189) which has established codesof ethics for acoustical contractors in that State.
Experience
The consultant and contractor should have experiencein noise control work in similar industrial situations toyours. There is nothing like a recommendation fromone of your colleagues in the industry! Be wary ofcontractors who have not carried out acousticaltreatments before because they may be unaware of theacoustical properties of the materials involved.
Range of services available
Use the list of services in the table above under thesubsection “Roles and Limitations”, as a checklist whenassessing what the prospective company may offer you.
Capability
In the case of a consultant, what noise measuring anddiagnostic equipment is to be used? A consultant whohas only a basic sound level meter cannot get as muchinformation as one who can carry out detailedfrequency analysis, vibration analysis, sound intensity
2. SELECTION OF
CONSULTANT OR
CONTRACTOR
MODULE 4: 6
analysis and other services. For a contractor, thequestion of capability centres on the workshop facilitiesand personnel available. The job may be too large, toosmall or too specialised.
Fees and availability
Most consultants would charge an hourly rate, up to anagreed ceiling beyond which further agreement needsto be made. You need to check whether the hourly rateincludes measuring equipment as well as time, and anyother charges which may accrue. Note that the hourlyrate will vary depending on the status of the personcarrying out the work. Contractors normally charge onan agreed lump sum basis, with variations as instandard building practice.
Having selected your consultant or contractor, you willneed to give them a clear brief, so that both of youunderstand exactly what services will be provided andwhat outcome you expect. The points listed underStage 1 will form the basis of the brief. However, theconsultant or contractor may have further thoughts onhow the brief should be structured, so you may finalisethe brief only after an initial meeting with theconsultant or contractor.
The brief may be incorporated into a formal contract ormay be in the form of a letter on which the contractualarrangements are based. It is quite common forconsultants to write their own brief as part of aproposal, or for contractors to write their own brief aspart of a quotation. As always, it is important to havethe brief in writing.
Constant liaison/supervision is one of the keys togetting the best from your consultant or contractor. Ifyou can be “on the spot” with information about theorganisation and work processes, establish contacts andhelp with access arrangements, the consultant orcontractor can make more efficient use of the time andcreate less disturbance in the organisation.
As the consultant’s or contractor’s work progresses, newoptions may emerge, requiring consultation withinyour organisation. In particular, keep the consultant
3 BRIEFING
CONSULTANT
OR
CONTRACTOR
4. LIAISON
AND
SUPERVISION
MODULE 4: 7
and contractor well-informed on the likely operationalstatus of the plant. They may, for example, be keen tolook at the plant during shutdown as well as whenoperational. Try to provide the most up-to-date adviceon likely timing of any special process for which theirpresence on site is needed.
By following this four-stage process in the use ofconsultants and contractors when undertaking noisecontrol work, you should be able to achieve the mostcost-effective solutions in your workplace. It is wise toconsult external expertise prior to spending a lot of timeand money doing-it-yourself, since the old adage, “thereis never enough money to do it properly, but alwaysenough to do it twice” is still true!
SUMMARY
MODULE 5: 1
MODULE 5: USING SURVEYS
Noise managersProduction/engineering staffEmployee representativesOHS committees.
Once a noise survey report has been prepared for aworkplace, the noise manager should be able to:
• define which parts of the workplace and workforcehave been surveyed;
• identify which employees are likely to be exposed tonoise above the exposure limits;
• describe the conditions under which the plant wasoperating at the time of the survey, comment onwhether or not this was typical, and estimate thelikely effects of other normal operating conditions;
• assess the level of risk of employees suffering anoise-induced hearing loss;
• identify in which areas, during which operations, orat which machines the employees are receiving themost significant noise exposures;
• provide relevant information to both managementand employees as to noise in the workplace, as partof a noise education programme;
• select appropriate personal hearing protection foremployees in noisy areas;
• define any remaining legal obligations which theemployer (or employees), may have to fulfil.
PURPOSE OF A NOISE SURVEYWHAT YOU NEED TO USE A SURVEYDEFINE SCOPE OF SURVEYIDENTIFY EXPOSED EMPLOYEESDESCRIBE PLANT OPERATING CONDITIONSASSESS RISK TO EMPLOYEESIDENTIFY AREAS OF HIGHEST EXPOSURESELECT HEARING PROTECTORSPROVIDE INFORMATIONDEFINE LEGAL OBLIGATIONSSUMMARY
OUTCOMES
CONTENTS
THIS MODULE
IS FOR
MODULE 5: 2
UNDERSTANDING AND USING NOISESURVEY REPORTS
A noise survey report is first and foremost a springboardfor action. It provides the basic technical informationabout the workplace to enable you to take the actionslisted under OUTCOMES on the previous page. Thenoise survey report contains measurements of the noiselevels (especially the A-weighted noise levels) to whichoperators are exposed and estimates of their typicaldaily noise exposure levels. The report may cover thewhole workplace or only part of it (for example, themachine shop or a new vehicle).
It may have been prepared in response to the need tocomply with the law or in response to a request fromthe employees for information on noise levels.
A noise survey report is not a noise control plan (seeStep 4 of the Core) or a noise policy (see Step 3 of theCore and Module 7: Noise Policy) for your workplace.These need to be developed from the information in thenoise survey report.
Above all, the noise survey report should not be seen asa menu for personal hearing protectors as though thiswere the end point of your noise management planning.
A noise survey report is unlikely to be written in a formsuitable for presentation “as is” to management andemployees. Relevant information will need to beextracted and presented in a different format. Forexample, the noise level results may need to betransferred onto a wall chart to show noise levels invarious areas, with a “temperature scale” to show whatthe noise levels mean.
Firstly, you need a basic grasp of noise terminology andhow noise surveys are carried out. Appendices 1 and 2of the Core list some of the terms you should know. Forfurther reading on noise measurement, see Bruel andKjaer Ltd.’s booklet Measuring Sound (Denmark, 1984)available from Reid Technology Ltd, PO Box 1898,Auckland. The methods of noise measurement and thebasis of calculations used in noise survey reports are
PURPOSE OF
A NOISE
SURVEY
WHAT YOU
NEED TO USE
A SURVEY
MODULE 5: 3
detailed in Australian Standard AS1269 Acoustics -Hearing Conservation, available from Standards NewZealand.
Secondly, you need a grasp of the regulation onoccupational noise. Approach the Occupational Safetyand Health Service to find out their requirements. Theymay have booklets or run short seminars explaining thelegislation.
The noise survey report should clearly set out, at thebeginning, which parts of the workplace or workforcehave been surveyed. For example:
This noise survey report on XYZ Bakery covers themain baking hall and adjoining preparation areas.There are approximately 80 staff employed in this area,including plant operators, packers and supervisors.The survey did not include the following people whoare to be the subject of a later survey:
• laboratory and technical staff;
• workshop and maintenance staff;
• drivers and vendors;
• office staff.
Employees likely to be exposed to noise above theexposure limit should he identified.
In small workplaces, the noise survey report may list allemployees likely to be exposed above the exposure limit.In medium to larger workplaces, this may have to beestimated from the results in the report. For example,if the report contains an assessment of two plantoperators, both of whom are exposed to noise above theexposure limit, then it can he assumed that the othereight operators performing similar tasks may also beexposed to noise above the exposure limit.
If noise exposures vary a lot over the day, or from day today, it is often possible to estimate an employee’s typical8-hour average exposure from the results in the report.
DEFINE SCOPE
OF SURVEY
IDENTIFY
EXPOSED
EMPLOYEES
MODULE 5: 4
Machine/Process Noise Level at Operator’s EarL
Aeq,T (dB(A))
Angle grinder 104
Power hacksaw 88
Chipping hammer 98
Welding 93
Ambient noise 85
You now estimate the typical duration for which theemployee is likely to operate those items in a typical“worst case” day, that is, angle grinder 1 hour, hacksaw1.5 hours, hammer 0.5 hour, welding 2 hours andambient noise for remainder of day (3 hours). Asdescribed in Appendix 2 of the Core of this ControlGuide, use Table 3 to assign a PNE to each of the abovecombinations of noise levels and durations asdemonstrated in the following table:
Noise level Duration PartialMachine/process LAeq,T (dB(A)) (hrs) noise exposure
(Pa2h)
Angle grinder 104 1.0 10.0
Power hacksaw 88 1.5 0.4
Chipping hammer 98 0.5 1.3
Welding 93 2.0 1.6
Ambient noise 85 3.0 0.4
Daily Noise Exposure = sum of partial noiseexposures = 13.7
The daily noise exposure is simply converted to theequivalent 8-hour noise exposure level using the sameprocess in reverse.
LAeq,8h
= 96 dB(A)
This value is then compared with the exposure limit.
The above example shows that it is possible to estimatean employee’s noise exposure for a given day’s duties,knowing the noise levels and duration of the varioustasks.
Sometimes, however, an employee’s exposure is likely tobe so variable that a typical duration for each task
MODULE 5: 5
cannot be assigned. In this case, it is often possible toassess the likelihood that the noise exposure exceeds theexposure limit. This can be done by taking the noiselevel results in the report and calculating the durationfor which one operation would need to be carried out tocause the exposure limit to be exceeded. To do this, useTable 3 in Appendix 2 of the Core in the following way:
• look up the Pa2 value for the noise level, (X);
• divide 1 by this value (1/X);
• the result is the time in hours beyond which theexposure limit will be exceeded.
Example (the exposure limit is LAeq,8h
85 dB(A))
Machine/process Noise level Time for exposure limit
LAeq,T (dB(A)) to be exceeded
Angle grinder 104 6 mins
Power hacksaw 88 4 hrs
Chipping hammer 98 24 mins
Welding 92 1.6 hrs
Ambient noise 85 8 hrs
Knowing that the employee is likely to spend at least 6minutes per day on the angle grinder, apart from othernoise exposure during the day, indicates that theemployee’s exposure is likely to be above the exposurelimit.
Note that there may be employees who spend time inthe area without operating the machines (for example,other staff and cleaners). You could assume that theseemployees are exposed to the “ambient level’ given inthe example.
Remember that exposure limits are also expressed interms of a peak noise level for impulsive/impactivesounds, as well as an 8-hour exposure level. In thiscase, any employee exposed to such a high level ofsound, even once in a day, should be counted as beingexposed above the exposure limit.
Using the results in the noise survey report in this way,you should be able to construct a picture of thoseemployees likely to be exposed to noise above theexposure limit. You could use this procedure for
MODULE 5: 6
identifying priorities for noise control and personalhearing protection and to establish which employeesare to be given audiometric testing.
A well-written noise survey report should describe theplant operating conditions at the time of the survey,indicate whether the conditions are typical and, ifrelevant, note the effects of other conditions.
A well-written noise survey report should include mostof this information. If you return to the above example,the noise level results in full should read thus:
Machine/process Noise levelLAeq,T (dB(A))
Angle grinder (100 mm Hitachi, grinding2 m length of 25 x 25 mm steel tubing) 104
Power hacksaw (cutting 6 m lengthsof 25 x 25 mm steel tubing) 88
Now look at these results critically. Consult others inthe workplace. Are these typical of the noisiestoperations that would take place? If not, you may needto have measurements carried out on the noisiesttypical operation. The factors you need to considerinclude:
• the size and type of material being worked on(larger hollow workpieces may radiate more noise);
• the rate at which work is being done (for example,blows per minute or motor speed);
• the number of machines operating together;
• presence or absence of extraneous noises (forexample, noisy equipment due for repairs or con-tractor on site);
• the amount of time employees would normallyspend in that area.
Look carefully at the situation of employees whose noiseexposure was found to be marginal, or just below theexposure limit in the survey report. Could any of theabove factors cause their exposure to exceed theexposure limit?
DESCRIBE
PLANT
OPERATING
CONDITIONS
MODULE 5: 7
In some cases you can estimate the effect of a change inoperating conditions. For example, a doubling in thenumber of blows from 60 to 120 per minute wouldnormally increase the LAeq,T
by 3 dB(A). However, youwill probably need to consult an expert in mostinstances, as these calculations can be very complex. Ingeneral, concentrate on the larger factors and don’t getdistracted by small differences in operating conditions.Keep in mind that you are trying to estimate theemployee’s noise exposure on a typical “worst-case” day,not under every possible set of conditions!
It may be useful to go further than just estimating thenumber of employees exposed above the exposure limit.Knowing that the risk of hearing loss exists even belowthe exposure limit and that it increases as the levelincreases, you may wish to estimate the likely extent ofhearing loss for a given level of noise exposure over anominated period of years. Appendix D of AS1269-1989gives a method for this type of assessment.
In developing a noise control plan, you will need toknow where the noise problems are. You can build upthis information by studying the workplace and thenoise survey report, (although you may not have to havea noise survey done before developing a noise controlplan).
A thorough noise survey report might give a list of somenoise control treatments required, especially anystraightforward items. If not, you can glean a lot ofinformation from the results by working through thefollowing steps.
Step 1
Look at the noise levels themselves and identify items ofplant or areas which are potentially:
• extremely hazardous (greater than 105 dB(A));
• hazardous (90 - 105 dB(A));
• marginally hazardous (80 - 90 dB(A)).
ASSESS RISK
TO
EMPLOYEES
IDENTIFY
AREAS OF
HIGHEST
EXPOSURES
MODULE 5: 8
Step 2
Look at the period of time over which each source islikely to operate, or the period of time the employee islikely to be exposed to that noise source. Use the noiselevel and exposure duration data to calculate partialnoise exposures, following the procedure outlined above(see the section “Identify Exposed Employees” above).
The higher the PNE, the more significant is the riskassociated with the operation. In the example the anglegrinder represented the greatest level of risk (PNE =10.0), followed by the welding operation (PNE = 1.6)and the chipping hammer (PNE = 1.3). Note thatalthough the welding operation was less noisy (93dB(A)) than the chipping hammer (98 dB(A)) the PNE,and therefore the associated risk, was greater because ofthe longer operating time. So, if the noise survey reportgives you results in terms of Partial Noise Exposures,use these to identify high-risk areas.
Step 3
Look at the number of employees involved in each highrisk area or operation. In general the greater thenumbers of employees at high risk, the higher thepriority in the noise control plan.
Some techniques for looking at these issues in greaterdetail and for comparing the effectiveness of variousnoise control options are discussed in Module 9:Evaluating Options.
The noise survey report should contain information onthe grading of areas or machines/processes and theappropriate personal hearing protectors required (seeModule 12: Personal Protection).
A noise survey report may give a list of personal hearingprotectors and the noise levels to which wearers wouldbe exposed. While this makes selection easy, rememberthat the “appropriateness” of any protector will dependon other factors as well, such as weight and clampingforce of earmuffs, compatibility with other headgear andcomfort. This is dealt with in more detail in Module 12:Personal Protection.
Finally, keep in mind that personal hearing protectionis no substitute for engineering noise control, since:
SELECT
HEARING
PROTECTORS
MODULE 5: 9
• the hazard is still there in the workplace;
• you can’t be sure exactly how much the risk hasbeen reduced;
• you are placing all the responsibility on the em-ployee.
A noise survey report is likely to be in too technical aform to be useful to most managers and employees,although this information forms a crucial part of thenoise education programme. Here are a few ideas forpresenting the information in a more accessible form:
• erect warning signs (standard warning signs aremandatory where personal hearing protection isrequired);
• summarise results on charts or wall posters;
• publish results in “in-house” newsletters orcirculars;
• use results for in-house training sessions;
• fix noise labels to machines where appropriate.
Copies of the noise survey report should always beavailable at the workplace for any employee, employeerepresentative, manager or health and safety inspector.
Having received a noise survey report you should makeyourself aware of any legal obligations relating to thereport itself. Apart from carrying out noise controlwork and providing personal hearing protection, theremay be requirements to:
• make copies available at the workplace;
• communicate the results to the health and safetyinspector;
• communicate the results to employees;
• repeat the noise survey after a period of 5 years.
In some cases, these requirements may be stated in thereport. You can check with your local branch ofOccupational Safety and Health for currentrequirements.
PROVIDE
INFORMATION
DEFINE LEGAL
OBLIGATIONS
MODULE 5: 10
Your noise survey report is a working document, aspringboard for achieving change in the workplace. Theway it is understood and used will have a significantbearing on the effectiveness of your noise managementprogramme.
A word of warning on the selection of personal hearingprotectors. It is tempting to go straight to the highest-performance protector, that is the one that reducesnoise the most, “to give employees the best protection”.There is a danger in over-protection since workers maynot hear warning sounds, they will remove theirprotectors when not exposed to the loudest noise andthe devices may be uncomfortable due to their weightand clamping force. In general, choose appropriatelygraded devices, that is, a device that has the samegrading as (or one grade higher than) the noise inquestion.
SUMMARY
MODULE 6: 1
MODULE 6: COSTS/BENEFITS
Chief executive officerNoise managerOther managersEmployee representativesOHS committee.
A consideration of the contents of this module shouldresult in:
• raised awareness of the costs of workplace noise;
• raised awareness of the benefits of workplace noisereduction;
• calculation of estimated annual financial losssuffered by the organisation as a result of noise;
• consideration given to including expenditure onnoise reduction as a permanent item in the organi-sation’s annual budget until noise has been reducedto acceptable levels;
• inclusion of this decision in the organisation’s noisepolicy.
OVERVIEW
INTRODUCTION
COSTS OF NOISE TO ORGANISATIONS
COSTS OF NOISE TO EXPOSED PERSONNEL
BENEFITS OF NOISE CONTROL FOR THEORGANISATION
BENEFITS OF NOISE CONTROL FOR EXPOSEDPERSONNEL
REFERENCED DOCUMENTS
THIS MODULE
IS FOR
OUTCOMES
CONTENTS
MODULE 6: 2
COSTS OF NOISE AND BENEFITS OFNOISE CONTROL
The costs of noise have usually been thought of only interms of compensation costs for noise-induced hearingloss (NIHL). This can make it difficult to justifyexpenditure on noise control because the benefits seema long way off. It is argued that people will keep comingforward with compensation claims for NIHL that wasactually caused years ago, so the benefits of noisecontrol expenditure won’t be realised for years. This isincorrect. Compensation costs are probably less than10 percent of the total costs of noise (see the table onpage 9 of this module). The benefits of noise controlcan be realised immediately in relation to absenteeism,morale, productivity, noise-related accidents andcorporate image; and in the short-term in relation toturnover and employee quality.
The material in this module is based on an analysis ofAustralian data using approaches developed in the USAand Sweden.
The USA approach is detailed in Richard K. Miller’sHandbook of Industrial Noise Management (1) and theSwedish approach in the Swedish Joint Industrial SafetyCouncil publication Working Environment andEconomy (2).
The following extracts from these references summarisethe overall approach:
There is an obvious trend in industry to improvethe working environment. With the increasedquality of life brought about in recent years, work-ers are becoming more reluctant to work in poorenvironments. Some industries are finding thatthey are losing top workers to nearby plants withair conditioned or sound-controlled facilities.Decreased productivity is currently a problem ofnational concern, and it must be recognised thatdecreased morale due to dissatisfaction with envi-ronmental conditions is a major contributor to theproblem. It is not a coincidence that many of the
OVERVIEW
INTRODUCTION
MODULE 6: 3
largest, most productive, and most profitableindustries in the country are also the quietest, andpossess the most pleasant overall working environ-ments.(1)
A well engineered working environment pays off.An investment which leads to efficient productionwith high product quality, a good working environ-ment and interesting work tasks is also the basis forhigher profitability. The reverse is also true, as apoor working environment reduces the company’sprofitability through increased absenteeism, higherpersonnel turnover, lower product quality andincreased production costs. Questions about theworking environment should not be seen as anisolated issue, but as an integral part of an organi-sation’s operations.(2)
What follows is an estimate of the financial costs toindustry of untreated workplace noise. New Zealandand Australian data are used where available butconservative estimates are based on USA data whereNew Zealand or Australian data are unavailable.
A number of hidden costs are associated with noise. Inaddition to compensation claims for industrial deafness,noise generates costs by means of its detrimental effectson work attendance, staff turnover, employee qualityand productivity. The data suggest these factors are ofgreater economic significance than compensation costsalone.
The role of noise in causing accidents is also considered.It is concluded that there are several ways in whichnoise can contribute to workplace accidents but thatinsufficient data are available to quantify the resultingeconomic losses.
Other non-quantifiable factors considered are thenegative effects on morale and the corporate image ofoperating an excessively noisy working environment.
New Zealand-wide, the estimated annual payout by ACCfor compensation claims for noise-induced hearing lossis $38,000.000. In Australia, the estimated annualpayout for compensation claims is $35,000,000.(3)
COSTS OF NOISE TO
ORGANISATIONS
ACC LEVIES/
INSURANCE
PREMIUMS
MODULE 6: 4
The actual cost to the community is estimated to betwice this, that is, $76,000,000, once account is taken ofall the other costs involved in rehabilitation.(4) Itfollows that the compensation system as a wholerequires an input of this magnitude to cover the costs ofclaims payouts and associated overheads. This inputcomes, of course, from the ACC levies levied onindustry.
Manufacturing industry accounts for approximately 50per cent of compensation claims for noise-inducedhearing loss.(5) It is a reasonable assumption that it alsoaccounts for 50 per cent of the $76,000,000compensation burden, that is, $38,000,000.
There were 242,000 employees in the manufacturingsector in New Zealand in 1993,(6) (1,042,400 inAustralia).(7) It is estimated that 26 per cent ofemployees in the manufacturing sector are at risk ofNIHL (by which is meant exposure to daily noiseexposure levels of 90 dB(A) or more)(8). This means that26 per cent of 242,000, or 62,900 manufacturingemployees were at risk.
Each employee at risk of NIHL represents acompensation insurance burden for the employer of$38,000,000/62,900, that is $604.
In Australia a further, indirect, cost burden is created byretired workers with occupational NIHL who do notclaim compensation for their condition but whoinstead, as pensioners, obtain free hearing aids andaudiological services through the CommonwealthGovernment’s Hearing Services Programme. In 1988-89, the total cost of this programme was approximately$29 million and pensioners comprised 72 per cent of itsclientele.(9) No data are available to indicate theproportion of pensioners using this service who do sobasically as a result of occupational NIHL, but it ispossibly quite large. Even at 25 per cent, the annualcost would be over $7 million. This burden is passed onto the community generally through the Australiantaxation system.
Loud noise has long been recognised as a source ofstress in the working environment. Noise exposure iscorrelated with workers’ reports of difficulties in
ABSENTEEISM
MODULE 6: 5
communication in the workplace, failure to hearimportant events, such as warning sounds, andannoyance.(10) In workplace surveys noise is often thechief complaint made about working conditions.(11)
Suppose, then, an employee feels unwell and iscontemplating whether to come to work or to take asick day. The prospect of having to spend the day inhigh levels of noise, with its associated stresses, couldoccasionally be the deciding factor in the employee’sdecision to take the day off.
There appears to be no published New Zealand orAustralian data comparing absenteeism in noisy andquiet working environments. In the USA, a NationalInstitute of Occupational Safety and Health (NIOSH)study(12) of 866 employees found that median absencerates for quiet (<80 dB(A)) and noisy (approximately 95dB(A)) areas were respectively 5 and 19 days a year.
Following introduction of a personal hearing protectionprogramme for the high noise group, their absencesdropped to a median of 9 days a year, a greatimprovement but still 4 days an employee per yearabove the median for the quiet group.
If the USA results are accepted as a guide, noise isresponsible for at least four extra days’ absence per yearper noise-exposed employee. This means that noisecauses the loss of four days’ production per year fromeach noise-exposed employee. The value of this lostproduction will, of course, vary from plant to plant andemployee to employee, but an average figure can beestimated as follows:
• There are approximately 235 actual working daysper year (250 less 15 days’ annual leave).
• Suppose the average salary per noise-exposed shopfloor employee is $22,000, then the average dailysalary is $22,000/235 = $93.60 per actual workingday.
• To allow for overheads and a profit margin, thevalue of an employee’s production must be greaterthan the employee’s salary. Suppose it is 1.5 timessalary. Then each lost employee-day represents aloss of 1.5 x $93.60 = $140.40.
• The annual loss per noise-exposed employee is fourtimes this amount, that is $561.60.
MODULE 6: 6
As pointed out above, noise is a significant cause ofemployee dissatisfaction with workplace conditions.Unless the labour market is very depressed, noise musttherefore have some influence on staff turnover rates.
Turnover is a well-recognised drain on productivity, asthe following analysis of resulting non-productiveactivities and costs shows.
Recruitment expenses include:
• costs of advertising vacancy;
• time spent interviewing applicants and selectingnew employee;
• costs of medical examination (if required);
• time spent introducing new employee to workplace,issuing tools, protective clothing;
• costs of audiometry;
• time spent training new employee.
Lost production costs include:
• lost production, or extra overtime costs, in theperiod between the departing employee leaving anda new employee starting;
• reduced output, or extra overtime costs, during anew employee’s training and learning period;
• any losses associated with increased number ofdefective or low-quality products produced duringthe new employee’s training and learning period;
• increased risk of accidents during learning period.
Although relevant field data are again unavailable, it isestimated that the total cost of losing one employee andreplacing them with another could approximate $1,000.
Suppose that noise is the determining factor in one staffturnover event per noise-exposed employee per ten yearperiod. Then, on the above reckoning, it would accountfor a loss of $1,000 for each noise-exposed employeeonce every 10 years, or $100 per noise-exposedemployee a year.
Because of their worth to employers, good-qualityemployees can to some extent pick and choose their
STAFF TURNOVER
EMPLOYEE
QUALITY
MODULE 6: 7
employment. Better employees tend to seek and holdjobs in organisations with superior working conditions.
This means that, all other things being equal, thenoisier the workplace the poorer the chances ofattracting the best employees. This too must have someeffect on productivity.
Even if the difference is as low as 1 per cent (that is thequality of employees in noisy workplaces is 99 per centthat of employees in quieter workplaces) it is worthconsidering. Assuming, as before, that the value of anemployee’s production is l.5 times the employee’swages, a 1 per cent decrement in productivity equals 1per cent of (1.5 x $22,000) = $330 per employee peryear.
Noise can directly influence productivity, though notalways consistently. Noise can heighten alertness andspeed up performance on some tasks, but it can slowperformance and increase error rates on others.(13) Moststudies in the area have investigated the effects ofreproduced or artificial noises on specific tasks inlaboratory settings. It is usually impossible to deducewhat the results imply for multiple and complex tasksin actual working conditions. A number of field studieshave claimed productivity improvements between 3.5and 30 per cent due to noise reduction. However, fieldstudies are seldom well-controlled in the scientificsense and it is difficult to know how much of theobserved improvement is due to noise reduction andhow much to other causes such as improved morale.The links between noise and productivity are complexbut the weight of evidence tends to support the industryexperience quoted above that “. . . many of the largest,most productive, and most profitable industries in thecountry are also the quietest . . .”(1)
Making the probably modest assumption that workersin excessive noise levels are 2 per cent less productivethan those who are not, it can be calculated (as in thesubsection “Employee Quality” above) that each noise-exposed worker represents a wastage of $660 per year.
PRODUCTIVITY
MODULE 6: 8
Noise can be a significant factor in accidentcausation.(14) Wherever safe working practices dependon voice communication, noise will be a threat to safety.People have been killed or injured as a result of failureto hear warning shouts.(15)
Noise can also make the consequences of an accidentworse than they otherwise might have been. A workerwhose hand was caught in manufacturing equipmentscreamed for help but was not heard because of thesurrounding noise. As a result he lost his hand.(16)
A review of noise and accidents by staff of the Instituteof Sound and Vibration Research in the UK concludedthat:
There is suggestive, although not conclusive,evidence that noise is at least a contributory factorin the occurrence of some accidents . . . the possi-ble link between noise and accidents provides astrong argument for the reduction of occupationalnoise levels in addition to that required to preventhearing damage.(17)
Unfortunately, there are no data on either the numberor likely costs of noise-related industrial accidents inNew Zealand or Australia. Nonetheless, the potentialfor such costs is obvious and must be kept in mindwhen considering the probable costs of excessive noisein the workplace.
Until noise hazards are removed from the workplace apersonal protection programme will be necessary.While personal hearing protectors may control the riskof hearing damage to some extent, dependingprincipally on usage rates, they do not remove the noisehazard. In addition, they may make only a marginal orno improvement in communication, may introducediscomfort, will almost certainly be less acceptable toemployees than noise controls and may provokeemployee resistance and complaints. It is thereforelegitimate to treat the cost of personal protectionprogrammes as a cost of untreated noise.
It is estimated that, on average, the cost of a personalprotection programme is about $110 per worker peryear. This represents the sum of the estimated annual
RISK OF
ACCIDENTS
PERSONAL
PROTECTION
PROGRAMME
MODULE 6: 9
costs of warning signs and labels ($10), hearingprotectors ($20), maintenance ($10), information andtraining ($20), supervision and management ($20) andperiodic hearing checks ($30).
Source of loss Estimated annual loss pernoise-exposed employee
($)
NIHL insurance (through levies) 604
Absenteeism 560
Staff turnover 100
Employee quality 330
Productivity 660
Personal protection programme 110
Total annual loss per noise-exposed employee $2,364
The average number of noise-exposed employees permanufacturing establishment is 7.6.(6) The averageannual loss per manufacturing establishment caused bynoise is therefore 7.6 x $2,364 = $17,966.
To estimate the probable annual noise costs in your ownorganisation:
Number of noise-exposed employee x $2,364 =$ ——— per annum
This sum is a minimum estimate, since quite cautiousassumptions have been involved in its derivation and nofinancial cost has been placed on some factors,especially costs arising from noise-related accidents.
The main costs borne by noise-exposed personnel havebeen summarised in step 1 of the Core and explained indetail in Module 10: Fact Sheets. In summary, noise-exposed personnel risk:
• permanent hearing loss and its personal and socialconsequences;
• permanent tinnitus (“ringing in the ears”);
• possible safety hazards;
SUMMARY OF
COSTS
COSTS OF
NOISE TO
EXPOSED
PERSONNEL
MODULE 6: 10
• communication problems in the workplace;
• annoyance, stress and fatigue.
Reduced risk of compensation claims
A reduction in the number of hearing losscompensation claims should ultimately reduce ACClevies.
Reduced risk of penalties
There will be a reduced risk of prosecution andpenalties in relation to:
• prosecution under the Health and Safety in Em-ployment Act 1992 for failing to provide a safe placeof work and for breaches of the noise regulation.
Reduced reliance on personal protection
Fewer people will need hearing protectors and thosewho still do may be equipped with lighter, morecomfortable hearing protectors which will improveacceptance and wearing rates. Even if protectorperformance is impaired as a result of poor fitting orpoor maintenance, the likelihood of hearing damagewill be less. If hearing protectors are removed for shortperiods, or even if not worn at all, there will be less riskof hearing damage.
Productivity improvements
Productivity will improve because of:
• reductions in absenteeism, personnel turnover andaccidents;
• an ability to attract higher quality employees;
• improvements directly related to a quieter workingenvironment.
Catalysing effect on other OHS programmes
A well managed noise reduction programme creates aclimate supportive of other health and safety initiativesand strengthens an organisation’s overall health andsafety programme. Much of the experience gained inplanning and implementing the noise programme willbe transferable to other health and safety issues.
BENEFITS OF
NOISE CONTROL
FOR THE
ORGANISATION
ECONOMIC
BENEFITS
NON-ECONOMIC
BENEFITS
MODULE 6: 11
Industrial relations
By providing concrete evidence of an organisation’scommitment to OHS, a good noise managementprogramme will contribute to improved industrialrelations.
Corporate image
Noise is a high-priority OHS issue (it is one of theOccupational Safety and Health Service’s priorityhazards) and a commitment to noise control givescredibility to an organisation’s health and safety image.
Exposed personnel will benefit because of:
• a reduced risk of hearing loss and tinnitus;
• the reassurance that their health and welfare isimportant to an organisation;
• improved communications in the workplace;
• less stress, annoyance and fatigue.
1. Miller, R.K., Handbook of Industrial NoiseManagement, The Fairmont Press, Atlanta,Georgia, 1976.
2. Swedish Joint Industrial Safety Council, WorkingEnvironment and Economy (in Swedish),Swedish Joint Industrial Safety Council,Stockholm, 1988.
3. National Occupational Health and SafetyCommission, Discussion Paper with Options for aNational Standard on Occupational Noise andDraft National Code of Practice for NoiseManagement and Protection of Hearing at Work,Australian Government Publishing Service,Canberra, 1989.
4. Bennett, B., “The Cost of Industrial DeafnessCompensation”, Proceedings of a NationalSeminar on Industrial Deafness, University ofNew England, Armidale, 1981.
5. National Occupational Health and SafetyCommission, unpublished data, 1989.
BENEFITS OF
NOISE
CONTROL FOR
EXPOSED
PERSONNEL
REFERENCED
DOCUMENTS
MODULE 6: 12
6. New Zealand Official Year Book 1994, StatisticsNew Zealand.
7. Australian Bureau of Statistics, ManufacturingIndustry Selected Items of Data byEmployment Size Australia 1987-88, AustralianBureau of Statistics, 1990.
8. Gibson, D.C. and Norton, M.P., “The economicsof industrial noise control in Australia,” NoiseControl Engineering, vol. 16, no. 3, pp. 126-35,1981.
9. Industry Commission, Aids and Appliances forPeople with Disabilities, Draft Report, IndustryCommission, Canberra, 1990.
10. Van Dijk, F.J.H., Souman, A.M. and De Vries F.F.,“Non-auditory effects of noise in industry VI. Afinal field study in industry”, InternationalArchives of Occupational and EnvironmentalHealth, vol. 59, pp. 133-45,1987.
11. Juhl Pedersen, O., “Noise and People”, NoiseControl Engineering Journal, vol. 32, no. 2, pp.73-8,1989.
12. Cohen, A., “The influence of a company hearingconservation programme on extra-auditoryproblems in workers”, Journal of SafetyResearch, vol. 8, no. 4, pp. 146-62, 1976.
13. Levy-Leboyer, C and Moser, G, “Noise effects ontwo industrial tasks”, Proceedings of the 5thInternational Congress on Noise as a PublicHealth Problem, vol. 3, pp. 43-8, 1988.
14. Noweir, M.H., “Noise exposure as related toproductivity, disciplinary actions, absenteeismand accidents among textile workers”, Journalof Safety Research, vol. 15, no. 4, pp. 163-174,1984.
15. Kinnersly, P., The Hazards of Work: How toFight Them, Pluto Press, London, 1973.
16. Environmental Protection Agency, Noise: AHealth Problem, Environmental ProtectionAgency, Washington, DC, 1978.
17. Wilkins, P.A. and Acton, W.I., “Noise andaccidents - a review”, Annals of OccupationalHygiene, vol. 25, no. 3, pp. 249-60, 1982.
MODULE 7: 1
MODULE 7: NOISE POLICY
Chief executive officerNoise managerOther managersProduction/engineering staffEmployee representativesOHS committee.
The purposes of this module are to:
• encourage the organisation to develop a writtennoise policy;
• suggest points the policy should address;
• suggest ways of developing the policy.
With the help of this module, the organisation shouldbe able to develop a written comprehensive noise policy.
WHAT IS A NOISE POLICY?
PURPOSES OF A NOISE POLICY
BENEFITS OF A NOISE POLICY
FACTORS TO TAKE INTO ACCOUNT
SPECIFIC ISSUES THAT MAY BE DEALT WITH
DEVELOPING THE ORGANISATION’S NOISE POLICY
USING THE POLICY
FURTHER READING
THIS MODULE
IS FOR
PURPOSE
OUTCOMES
CONTENTS
MODULE 7: 2
DEVELOPING A NOISE POLICY FORYOUR WORKPLACE
A noise policy is a document laying down the generalrules the organisation intends to follow in dealing withits noise problems. The most serious of these problemsis the presence of hazardous noise (sufficient to causehearing damage) in working areas. Noise can, ofcourse, cause problems even when it does not pose athreat to hearing (for example, it can create difficultiesin communication or concentration in office areas orprovoke complaints from the organisation’s neighbours)but these problems are outside the scope of thismodule.
The preparation of this module was facilitated byreference to the noise control policy developed by theNoise Management Team at BP Refinery (Kwinana) PtyLtd., Western Australia.
The organisation’s noise control goals should bespecified, for example:
• to ensure that no employee’s 8-hour average noiseexposure level (LAeq,8h) exceeds 90 dB(A) in 1997 and85 dB(A) by 2000; and
• to ensure that no employee is exposed to impulsenoise with a level exceeding 140 dB (Unweighted)Peak.
Preferred methods of controlling risk should bespecified, for example:
• Wherever workable, noise levels of existing plantwill be reduced by engineering means to achievethe above goals.
• Where it is not immediately possible to reach goalsby engineering means, exposure duration will berestricted.
WHAT IS A
NOISE
POLICY?
PURPOSES OF A
NOISE POLICY
SPECIFY GOALS
SPECIFY PREFERRED
CONTROL METHODS
MODULE 7: 3
• The wearing of personal hearing protectors may benecessary as an interim measure.
• Noise limits will be specified for new plant andequipment so that noise levels in working areas areprogressively reduced to the point where hearingprotectors are unnecessary.
Arrangements for achieving the specified goals shouldbe detailed, for example:
• A member of management will be appointed noisemanager to oversee and coordinate the noisemanagement programme.
• A noise working group, including employee and/oremployee representatives, will be set up to helpdevelop the noise control programme.
• An ongoing information and training programmeabout noise and its effects, noise control andpersonal hearing protection will be organised formanagers, supervisors and workers.
• Following a preliminary noise audit, a noiseconsultant will be called in to advise on noisecontrol options.
The responsibilities of managers, supervisors andemployees should be stated, for example:
• Managers are responsible for organising the noiseprogramme in areas under their control, preparingbudget estimates for noise control and ensuringthat their staff receive adequate information andtraining.
• Supervisors are responsible for monitoring the day-to-day operation of the noise programme, ensuringthat purchase requests for equipment and powertools specify the quietest workable item,monitoring the use and condition of noise controldevices and hearing protectors and maintainingrelevant records.
• Employees are responsible for attending noiseinformation and training sessions, using noisecontrol equipment and personal hearing protectors
DETAIL
ADMINISTRATIVE
ARRANGEMENTS
DEFINE
RESPONSIBILITIES
MODULE 7: 4
where necessary and reporting equipment defectsand problems to supervisors. Employees are invitedto nominate for membership of the noisecommittee and to participate in the development ofthe noise control programme.
In addition to the major points listed above, a wellthought out noise policy can serve a number of otherpurposes, including the following:
• Noise has been a feature of the industrial scene forso long that it tends to be accepted as an inevitablepart of many jobs. This attitude needs to bechallenged. A noise policy that sets definite noisecontrol goals will create such a challenge and putnoise “on the agenda” of relevant groups in theorganisation.
• A noise policy helps integrate the noise programmewith the rest of the organisation’s operations. Ifnoise is made a specialised area, it is in danger ofbeing regarded as the province only of specialists.On the other hand, if “think quiet” and “buy quiet”are fully integrated into the organisation’soperations, they stand a better chance of success.
• The process of working out a noise policy can helpidentify areas where arrangements need to be madefor coordination (for example, budgeting for noisecontrol needs to be integrated with overallbudgeting; a system is needed to keep the noisemanager informed of proposed equipmentpurchases).
• A forward-looking policy, especially one that givesclear priority to workable engineering controls,provides the strongest support for the introductionof personal hearing protection. Employees aremore likely to cooperate in a personal protectionprogramme if they can see there are plans toprogressively reduce noise to non-hazardous levels.
• The declaration of management commitment,embodied in a noise policy, helps create a positivehealth and safety climate in the organisation.
• It is a basic reference point for planning and fornoise information and training programmes withinthe organisation.
BENEFITS OF A
NOISE POLICY
MODULE 7: 5
• It promotes good industrial relations byacknowledging the value of employee participationand ideas.
The major factors that need to be considered indeveloping a noise policy are:
• the organisation’s legal obligations under theHealth and Safety in Employment Act and Healthand Safety in Employment Regulations;
• the resources (for example, technical expertise andfinances) at the organisation’s disposal;
• any occupational health and safety policies and/oragreements with employees or their representativesalready in place in the organisation;
• the costs, benefits and effectiveness of variousoptions (see Modules 6: Costs/Benefits and Module9: Evaluating Options).
Some key issues, such as setting a noise exposurestandard and adopting a “buy quiet” purchasing policy,were mentioned above. Other points that may need tobe covered, again with examples of possible policystatements, are given below.
Noise control in temporary work sites
Any temporary work site shall be suitably located orscreened to ensure that noise levels generated do notadversely affect employees’ hearing. If necessary, entryto such sites shall be restricted to personnel wearingappropriate graded hearing protectors.
Design of new work areas
New work areas shall be designed and laid out so thatemployee noise exposure is maintained at the lowestworkable level.
Purchasing of new plant and equipment
Noise emission will in future be an important factor inthe selection of new plant and equipment. So far as isworkable, the quietest available item shall be favouredfor purchase.
FACTORS TO
TAKE INTO
ACCOUNT
SPECIFIC ISSUES
THAT MAY BE
DEALT WITH
MODULE 7: 6
Warning signs
Working areas and equipment requiring the use ofhearing protectors shall be clearly identified byappropriate signs or labels.
Maintenance
All noise control fixtures (for example, seals, vibrationmounts and silencers) will be regularly inspected andmaintained to ensure that noise emission is kept to aminimum. Training sessions in basic noise control willbe organised for maintenance staff.
Work procedures to reduce exposure
Work procedures will be designed to minimise noiseemission and ensure that as few people as possible areexposed to high levels of noise.
Protection of contractors and visitors
Contractors and visitors to the organisation shallcomply with the noise control and personal hearingprotection procedures prescribed for employees.
Employees visiting elsewhere
Employees working at other employers’ premises (forexample, carrying out maintenance work) shall complywith noise control procedures in operation there anduse hearing protectors if necessary.
Audiometry
Audiometric (hearing) testing shall be offered toemployees according to the requirements of the Healthand Safety in Employment Act. Each employee shall beprovided with a record of his or her test results. Releaseof the test results to other persons shall be inaccordance with the legal requirements.
Budgeting
Estimates of the amount of funds necessary for theimplementation of this policy shall be included in theorganisation’s budget each year with a view to ensuringprogressive reduction and, where possible, ultimateelimination of noise hazards.
Regular review of policy
This policy shall be reviewed annually, at which timesuggestions for improvement will be invited from allinterested persons.
MODULE 7: 7
It is essential that senior management is involved in thedevelopment of the organisation’s noise policy and iscommitted to seeing it put into effect. The reasons arethat:
• top management controls the workingenvironment and is legally responsible forcontrolling any hazards it contains;
• top management has the final say in the allocationof funds and other resources and thereforeeffectively controls the extent to which the policy isput into practice;
• experience and research shows that topmanagement support is vital to the success of noisecontrol programmes.
Requirements that employees be consulted in thedevelopment of health and safety policies and systemsare now part of the Health and Safety in EmploymentAct. The reasons for this are:
• a policy is much more likely to be accepted andfollowed if the people it affects have a say indeveloping it;
• it is likely to be more relevant and effective becauseof the direct input of those affected.
There are other reasons for consulting employees andinvolving them in the development of an organisation’snoise policy. They have an intimate knowledge of themachines and work practices that create noise, and areusually an excellent source of ideas for possible controlmethods. Even when solutions are proposed by others,such as noise consultants or contractors, it is importantto seek the views of employees before installation tocheck that work flow and maintenance access will notbe adversely affected.
Once the noise policy is completed, don’t file it away,but:
• post it on notice boards to inform those concernedand demonstrate the organisation’s commitment toemployees’ health and safety;
DEVELOPING THE
ORGANISATION’S
NOISE POLICY
MANAGEMENT
EMPLOYEES
USING THE
POLICY
MODULE 7: 8
• use it in training new managers, supervisors andoperators in their responsibilities;
• use it to promote the organisation’s image;
• mention it when job vacancies are being advertisedto attract good-quality staff;
• use it as a reference when developing other OHSpolicies;
• have it on hand when a health and safety inspectorcalls to show what the organisation is doing tomeet its legal obligations.
Occupational Health, Safety and Welfare Commission ofWestern Australia, A Code of Practice for Noise Controlin the Workplace, Occupational Health, Safety andWelfare Commission of Western Australia, Perth, 1989.
WorkCover, South Australia, Managing Health andSafety at Work, WorkCover, South Australia, Adelaide,1989. (Also released by WorkCover Authority of NSW,Sydney, 1989).
Occupational Health and Safety Authority of Victoria,Code of Practice for Noise, No 17, 1 October 1992,Occupational Health and Safety Authority, Victoria,Australia.
Occupational Safety and Health Service, NZ, ApprovedCode of Practice for the Management of Noise in theWorkplace, Occupational Safety and Health Service,Department of Labour, New Zealand.
FURTHER
READING
MODULE 8: 1
MODULE 8: BUY QUIET
Noise managerProduction/engineering staffPurchasing staff.
The purpose of this module is to:
• illustrate a typical buy quiet purchasing procedure;
• provide guidelines for the preparation of noisespecifications;
• show how to calculate the maximum acceptablenoise level for new equipment;
• show how to interpret noise information providedby suppliers;
• discuss key policy and procedural issues.
INTRODUCTION
BASIC BUY QUIET RULES
PURCHASING PROCEDURE OVERVIEW
POLICY AND PROCEDURAL ISSUES
FURTHER READING
THIS MODULE
IS FOR
CONTENTS
PURPOSE
MODULE 8: 2
BUY QUIET PURCHASING POLICY ANDPROCEDURES
Increasingly, New Zealand and overseas occupationalhealth and safety legislation requires designers,manufacturers and suppliers of industrial plant andequipment to minimise hazards, such as excessivenoise, associated with their products, and to provideinformation about potential hazards to prospectivepurchasers. In addition, complementary legalobligations have been imposed on employers to ensurethat any plant they purchase is as free as possible fromhazards to employees. There is thus strong legislativebacking for buy quiet programmes.
Even so, noise is still often overlooked when newmachinery is purchased, with the result that theworking environment is needlessly noisy. Ignoringnoise at the purchasing stage also indicates inefficientmanagement, since the manufacturer can, in mostcases, reduce the noise level of a machine more cheaplyand effectively during manufacture than the purchasercan afterwards, as illustrated in the following example.
A manufacturer of plastic bottles required two new blowmoulding machines. A type of moulder was chosen assuitable and two were ordered. While the company gaveno thought to noise, it was the supplier’s practice toprovide information on sound levels produced by theirmachines. A value of 85 dB(A) was quoted as the noiselevel one metre from the moulder.
The supplier also offered optional noise controlequipment on the machine which would reduce thenoise level to 79 dB(A) at extra cost. The plasticscompany considered this an unnecessary expensebecause the 85 dB(A) noise level seemed low enough tocomply with the noise legislation.
The new moulders were installed side by side along awall but, as soon as they commenced operation, thepackers nearby complained about the high level of noiseand the fact that they were no longer able to hear theradio. They were given hearing protectors but thesewere not always worn.
INTRODUCTION
EXAMPLE:
SAVINGS FROM
NOISE CONTROL
AT DESIGN STAGE
MODULE 8: 3
Noise levels were measured around the moulders and atthe packing table, with the following results:
Position Noise level
Between moulders (at 1.0 m) 91 dB(A)
At packing table (2.5 m) 89 dB(A)
The end result was that the company had to fit noisecontrol treatments to the moulders, which proved to bemuch more expensive than if the supplier had beenallowed to incorporate the noise control features in thefirst place.
Note that noise levels measured after the machines wereinstalled were greater than those which the supplierquoted. Some of the reasons why this might occurinclude:
• installation (for example, mountings) not accordingto supplier’s specifications;
• there were different loads, materials, speed or otheroperating conditions;
• non-standard noise measuring techniques wereused.
In the example of the manufacturer of plastic bottleshowever, the reasons were more straightforward, asindicated below.
Reverberation
The noise levels quoted by the supplier had beenmeasured in a room which had very little reverberation,unlike the factory environment. In the factory, soundreflections from the back walls, ceiling and otherequipment increased the overall noise level created byeach machine from 85 to 88 dB(A).
Two machines were placed side by side
When two equally loud noise sources are addedtogether, the result is an increase of 3 dB(A). Twoadjacent 88 dB(A) sources would be expected to producean overall noise level of 91 dB(A), just as themeasurement showed.
MODULE 8: 4
Properly handled, the purchase of new plant is anopportunity for cost-effective noise control. Tocapitalise on this opportunity, two basic rules need to befollowed:
• invitations to tender for the supply of new plantshould specify a maximum acceptable noise level;
• if plant is to be purchased without tender, noiseemission data should first be obtained from poten-tial suppliers.
The aim in both cases is to enable competing productsto be compared with one another and assessed inrelation to the organisation’s noise goals. Theremainder of this module explains how to apply theserules in practice.
Flow chart 1 provides an overview of a typical procedurefor purchasing an item of industrial equipment, takingaccount of its noise emission in the process. Thefollowing explanations and comments relate to thelettered points on the flow chart.
(A) The chart commences at the point where theneed for a new item of equipment becomesapparent.
(B) The first question is whether the item fallswithin the scope of the buy quiet policy.
(C) If it does not, normal purchasing action canproceed.
(D) If it does, this is a good time to consider whetherthere is scope for changing the process forwhich the machine is required to an intrinsicallyquieter process (for example, changing fromnailing to gluing). A review of the exact natureof the need and of the possibility of substitutinga quieter process is therefore suggested at thispoint.
(E) If process substitution is feasible the purchase ofdifferent equipment may be necessary, leadingback to the question whether the newequipment falls within the scope of the buyquiet policy.
BASIC BUY
QUIET RULES
PURCHASING
PROCEDURE
OVERVIEW
MODULE 8: 5
(F) It sometimes happens that a thoroughexamination of the need for new equipmentreveals an unexpected and better solution. Forexample, a foundry had a severe noise problemarising from a finishing process applied tocastings. Critical examination of the need forthis process led to the discovery that thepurchaser of the castings was prepared to acceptthem unfinished for a slightly lower price. Thesolution removed the need for the process, wascost-effective for both companies and eliminateda severe noise problem at the foundry.
(G) If substituting a quieter process is not feasible,the next step is to calculate the maximumacceptable noise level that the new machine canbe allowed to introduce into the workplace. Amethod for making this calculation is explainedbelow (see “4 Maximum acceptable noise levels”in the next section and Flow chart 2).
(H) The next steps depend on the significance of thepurchase in relation to the organisation’s overallnoise problems. As explained in Step 4 of theCore Module, the classification of the purchaseas major or minor is based on the number ofitems to be purchased, their cost, estimateddaily usage and likely effect on workplace noiselevels.
(I) For major purchases, such as significant itemsto be purchased by tender, a noise specificationwill be necessary. If the organisation possessessufficient in-house expertise, a specification maybe prepared internally. See “3 Noisespecification” in the next section for the mainissues to be covered. Organisations lacking thenecessary expertise would be well advised toenlist the aid of a consultant. This isparticularly important if it is proposed toundertake noise emission verification testsfollowing installation, since the supplier willneed to be informed in advance of the technicaldetails of the tests to be conducted.
(J) For relatively minor items for which a formalspecification would be inappropriate, potentialsuppliers can be contacted directly and re-
MODULE 8: 6
quested to include noise details in the productnoise information, and asked specifically aboutnoise control options and accessories, which arebecoming more common as equipment manu-facturers respond to the increasing demand forquieter products.
(K) Noise information provided by suppliers must beevaluated carefully. The supplier’s noise meas-urements may have been made in a differenttype of acoustical environment and underdifferent operating conditions from those of theproposed installation. In addition, noise levelsmay be reported in terms of sound power levelsor sound pressure levels. Flow chart 3 showshow to take account of these factors whenestimating, from noise data provided by a pro-spective supplier, the workplace noise level likelyto result from installation of a particular item ofequipment.
(L) For items which, according to informationprovided by tenderers/suppliers, meet the noiselimit requirement, the next issue to consider iswhether to place a purchasing order.
(M) If no tendered item meets the requirement,tenderers can be requested to estimate the costof appropriate noise control measures andsubmit new proposals.
(N) Consideration of these proposals and, if neces-sary, further negotiation, will finally lead to thepoint where an acceptable proposal is receivedor it becomes clear that the specified noise limitcannot be met, in which case consideration willneed to be given to post-installation site controlmeasures (for example, acoustical absorption orbarriers), job rotation and personal protection.
(O) If there is no option but to order an item thatfails the original specification, it is advisable topurchase whatever noise controls/accessoriescan be afforded so that the supplied item has thelowest possible noise emission. This will makethe design of site noise controls easier, minimisetheir cost and minimise reliance on personalprotection.
MODULE 8: 7
Yes
Major or minor purchase
Request noise information from suppliers
Work out maximum acceptablenoise level for new equipment
Use flow chart 3
ComplianceUnacceptable Not feasible Acceptable
Non-noise requirementsDecision to order
Need for additional equipment
Within sope of buy quiet policy?
Is a quieter process feasible?
Major Minor
Prepare specification& invite tenders
invite tenders
Need for alternativeequipment?
Proceed to change toquieter process
Normal purchasing procedure
Use flow chart 2
Evaluate tenders Evaluate noise information
Is requirement met?Is requirement met?
Negotiate noise reduction. New tender/proposal
submitted
Consider new tender/proposal
Are noise levels to be measured?
Noise levels measured
Fails specification.Unacceptable
Require noise reduction by supplier to comply with
specification
Acceptable
Accept delivery
Is it worthwhile approaching other
suppliers?
Approach other suppliers
T U
No
Yes
S
O R
N
Q
P
No Yes
M
LNo
Yes YesNo
Yes
No
Yes
NoNo
A
C
B
ED
FG
H
I J
KK
FLOW CHART 1: BUY QUIETPURCHASING PROCEDURE
MODULE 8: 8
(P) If the suppliers originally approached are unableto offer equipment meeting the specification,consider approaching others. There can be widevariations in the noise output of competingmachines and it pays to shop around.
(Q) As with tenders, the point will sooner or later bereached where a machine meeting the require-ment is found or it is apparent that no availablemachine is likely to meet the requirement.
(R) The decision to order will, of course, be basednot only on noise emission but on significantnon-noise factors such as productivity, cost andother occupational health and safety issues.
(S) For major purchases, it is common to arrangefor the noise levels of the equipment to bemeasured to verify the supplier’s claims.
(T) If the measured noise levels fail to meet theagreed specification, the supplier should berequired to rectify the problem and the noiselevels should be re-measured to verify that theresult is acceptable. In cases of this type, theassistance of a consultant, especially if theconsultant was involved in preparation of thespecification, will be highly valued.
(U) Once an acceptable result is achieved, formalacceptance of delivery can go ahead.
Decisions that have to be made at various points in thepurchasing procedure raise policy and procedural issuesfor an organisation. These issues are discussed below.
What are the respective roles of the productionengineer, noise manager and purchasing officer?Naturally these will vary from organisation toorganisation but typical roles are described below:
Production engineer
The production engineer should:
• establish the need for new equipment;
• question whether a quieter process could be substi-tuted;
POLICY AND
PROCEDURAL
ISSUES
1. ROLES
MODULE 8: 9
• participate in the ultimate decision to order equip-ment.
Production engineer in association with noise manager
The production engineer should, in association with thenoise manager:
• specify the maximum acceptable noise level;
• assist with the preparation of specification andtender documents;
• evaluate noise information provided with tenders/quotes;
• participate in the decision to order equipment;
• negotiate with suppliers for additional noise controlas necessary;
• where required, arrange for noise measurementsfor evaluation and acceptance purposes;
• participate in the decision to formally acceptdelivery of equipment.
Noise manager
The noise manager should coordinate theimplementation of the buy quiet programme withoverall budget planning and with other parts of anorganisation’s noise management programme,especially the plant maintenance and replacementprogramme.
Purchasing officer
The purchasing officer should:
• check whether the item to be purchased is withinthe scope of the buy quiet policy;
• ensure that buy quiet procedures are followedwhere appropriate.
Which items fall within the scope of the buy quietpolicy?
While the specific items will vary from industry toindustry, buy quiet procedures should apply to allpotentially noisy equipment. Even powered hand toolsare important because they are a significant source of
2. BUY QUIET
MODULE 8: 10
excessive noise in many workplaces. If the size of theorganisation warrants it, consider compiling a specificlist of the potentially noisy items in your industry/enterprise to simplify the purchasing officer’s job.
What should be provided in a noise specification?
Specify the maximum acceptable noise level at aspecified position (or positions) when the machine isoperating under specified operating and acousticalconditions.
Noise level
The basic noise level to specify is the equivalentcontinuous A weighted sound pressure level (LAeq,T
)measured over a complete operating cycle (or theaverage of several cycles).
For equipment which is likely to emit high-levelimpulse noise (explosive-powered tools, impact devicessuch as presses) it may also be necessary to specify amaximum value of linear (unweighted) peak soundpressure level. The Health and Safety in EmploymentRegulations specify a maximum linear (unweighted)peak sound pressure level of 140 dB for occupationalexposure. This is an area where expert advice may beneeded.
Position
The position usually specified for noise measurementsis the operator’s position. However, for some machines(such as a machine for which there is no fixed operatorposition or a machine with a built-in operator’senclosure) it may be important to know the noise levelsat other points around the machine so that exposure ofthe operator, and the effects on others in the workplace,can be properly assessed. In these cases, specify thatnoise should be measured at points around the machineat a height of 1.5 metres above the floor and/or accessplatform(s) and 1.0 metre from the machine itself,ignoring small projections.
Operating conditions
The operating conditions to be specified depend on thenature of the machine and its intended use and include
3. NOISE
SPECIFICATION
NOTE:
MODULE 8: 11
such factors as speed, load, tooling, material beingprocessed and feed rate. Specify whatever conditionsare likely to result in the highest noise emission.
If it is not known what these might be, specify a rangeof typical operating conditions and base decisions onthe highest level.
Acoustical conditions
The acoustical conditions may be specified in threeways:
• The first option is to specify that the noise of themachine is to be measured under agreed conditionsin an environment similar to the proposed installa-tion site. In practice, the manufacturer’s or suppli-er’s workplace will often meet this requirement.
• A second option, appropriate for major purchasesby tender, is to specify that the maximum accept-able noise level is not to be exceeded when themachine is installed and operating in yourworkplace. This puts the onus on the manufacturerto take the acoustical characteristics of yourworkplace into account when responding to thetender invitation. In order to do this, the tenderershould inspect the installation site. If unable to doso, the tenderer would need to ask for relevantdetails such as the dimensions of the installationsite, the size and placement of nearby machines,benches and other fittings and the nature of floor,wall and ceiling materials. If a tenderer neitherinspects nor requests details, treat the tender withcaution.
• A third option is to specify that the noise of themachine is to be measured in a standard acousticalenvironment, such as one of those defined in arelevant New Zealand, Australian or InternationalStandard for machine noise measurement. Unlessyou are knowledgeable and experienced, you willneed expert help to select an appropriate standardand to interpret the results.
How do we work out the maximum acceptable noiselevel to include in a specification?
4. MAXIMUM
ACCEPTABLE
NOISE LEVEL
MODULE 8: 12
Fundamentally, this will be determined by the noiseexposure level the organisation sets as its goal forworking areas. As the case study in the “Introduction”shows, however, in order to keep workplace noise belowa certain limit, the noise output of individual pieces ofmachinery will usually need to be well below that limit.
Flow chart 2 outlines a step-by-step procedure forcalculating the maximum acceptable noise level for agiven installation site. The following comments refer tothe lettered points on Flow chart 2.
(A) In Box 1 enter the noise exposure goal[LAeq,8h
] that the organisation has set forworking areas.
(B) In Box 2 enter the present noise expo-sure level [L
Aeq,8h] at what will be the
operator position of the new machine,measured when the machine it is toreplace is not running.
(C) If the value in Box 1 exceeds the value inBox 2 (which means the present noise inthe area is below the goal), use the“Subtracting Decibels Table” on the flowchart to subtract the level in Box 2 fromthe level in Box 1 and enter the result inBox 4.
For example, if the level in Box 1 is 85dB(A) and the level in Box 2 is 80 dB(A),by using the “Subtracting DecibelsTable” the level to be entered in box 4 is83 dB(A).
(D) If the value in Box 2 exceeds the value inBox 1, the present noise in the area isabove the goal and therefore needs to bereduced. Estimate the level that willexist in the area after feasible engineer-ing controls have been installed andenter it in Box 3.
(D1) If the value in Box 3 is lower than thevalue in Box 1 (that is, anticipatedengineering controls will reduce thenoise in the area below the goal), use the“Subtracting Decibels Table” to subtractthe value in Box 3 from the value in Box
MODULE 8: 13
1 and enter the result in Box 4. Theresult is the maximum noise exposurelevel that can be introduced into thetreated noise environment withoutcausing the noise goal to be exceeded.
(D2) If the value in Box 3 is higher than thevalue in Box 1 (that is, after the installa-tion of feasible controls the noise in thearea will still exceed the goal), reducethe value in Box 3 by 10 dB(A) and enterthe result in Box 4. This will ensurethat after feasible controls have beenintroduced, installation of new equip-ment will have a minimal effect (theincrease will be less than 0.5 dB(A)) onthe noise exposure level in the area.
(E) Subtract 0, 3 or 5 dB(A) from the valuein Box 4, depending on whether 1, 2, or3 or more machines respectively will beinstalled either now or in the future,and enter the result in Box 5. Thiscorrection allows for the additive effectsof noise from adjacent sources.
(F) The value in Box 5 is the maximum levelthat can be tolerated from an individualmachine over its working lifetime.
(G) Since the noise emitted by a machinenormally increases with wear and tear, itis desirable to specify for a new machinea somewhat lower limit than the calcu-lated maximum acceptable value. Acorrection of 2 dB(A) allows a smallmargin for wear and tear and producesthe final result in Box 6.
(H) This is the maximum acceptable noiselevel to specify for a new machine.
MODULE 8: 14
FLOW CHART 2: CALCULATING THEMAXIMUM ACCEPTABLE NOISE LEVEL
FOR A NEW MACHINE
Organisation's noise level goal for working area
______ dB(A)
If value in box 1 is higher than value in box 2
______ dB(A)
If value in box 2 is higher than value in box 1
Present noise level in area where machine is
to be installed
A B
C D
Estimate reduced noise level in area after introduction of feasible engineering controls (ideally at least 2 dB(A) below
the value in box 1 to allow for noise of new machine)
BOX 2BOX 1
Estimated level after noise
controls
______ dB(A)
Is the value in box 3 lower or higher than value in box 1
BOX 3
Use table below to subtract level in box 2
from level in box 1
Use table below to subtract level in box 3
from level in box 1
Subtract 10 dB(A) directly from the level in box 3.
Do not use table
1 machine 2 machinesmore than 2
machines
No adjustment to box 4 Subtract 3 dB(A) directly from the
value in box 4.Do not use table
Subtract 5 dB(A) directly from the
value in box 4.Do not use table
______ dB(A)
This is the maximum additional noise level that can be introduced by new
equipment
Is is the only new machine to be installed or are others to be installed
in this area?
______ dB(A)
Specify this value as the maximum acceptable noise
level for a new machine
______ dB(A)
This is the maximum noise level that may be introduced
by a single machine
Subtract 2 dB(A) to allow for machine wear and tear.
Do not use table
Lower Higher
BOX 4
D1 D2
E
BOX 5F
G
H BOX 6
Subtracting Decibels
If levels differ by: Subtract from higher level:
10 dB or more6 - 9 dB4 - 5 dB3 dB2 dB1 dB
0 dB1 dB2 dB3 dB5 dB7 dB
MODULE 8: 15
The calculation method in flow chart 2 ensures that thenew machine can be used for up to 8 hours per daywithout causing the noise exposure goal to be exceeded.If it is certain that the machine will be used for fewerhours every day, higher noise levels, calculatedaccording to the 3 dB rule mentioned in Appendix 2 ofthe Core, could be tolerated without infringing thenoise exposure goal. For example, if the machine willnever be used for more than 2 hours a day, a maximumacceptable noise level 6 dB(A) higher than the valuecalculated in Box 6 (for 8 hours) would be tolerable.
Generally, in cases where a machine will he used (orpeople will he exposed to its noise) for less than 8 hoursa day, consider specifying a range of acceptable noiselevels encompassing its expected actual use and itspotential daily use. If the value in Box 6 is 78 dB(A) butthe machine will probably never be used more than 2hours a day, specify 78 dB(A) as the maximum preferredlevel, thus allowing for increased use/exposure at sometime in the future, say as a result of expansion, and 84dB(A) as the maximum acceptable level.
When comparing noise emission levels quoted bysuppliers with your maximum acceptable noise level,check the conditions under which the supplier’s noisemeasurements have been obtained. Noise levelsappearing in a supplier’s data sheet may have beenmeasured under non-representative conditions (forexample, a light to medium load on a machine installedin non-reverberant surroundings). At your workplace itis more likely that the surroundings will be reverberantand that the machine will be run at full load. To allowfor these effects, add 4 dB(A) to the supplier’s noisemeasurements unless it is clear that they were madeunder typical working conditions.
How can we work out from a supplier’s noiseinformation sheet how much noise their machinewould introduce into our workplace?
Both International and Australian standard methods arenow available for measuring and describing the noiseemission of industrial machines. It is best if suppliers’
NOTE 1:
NOTE 2:
5. USING
SUPPLIERS’ NOISE
INFORMATION
MODULE 8: 16
noise data have been measured according to one ofthese standards. Measurements made according toother procedures may, however, be acceptable ifperformed by a competent person according to a clearlydefined procedure.
Flow chart 3 presents a method for using a supplier’snoise information to estimate the amount of noise agiven machine will introduce into the workplace:
(A) Enter the supplier’s noise measurement resultin Box 1.
(B) Refer to the supplier’s noise information sheetto determine whether the noise was measuredas a sound pressure level or a sound powerlevel.
(C) If measured as a sound pressure level, make noadjustment. However, if supplier’s soundpressure level data are for positions at largerdistances than the operator’s location, seekexpert advice.
(D) If measured as a sound power level, subtract 8dB(A) from the value in Box 1 and enter theresult in Box 2.
(E) Refer to the supplier’s noise information sheetfor a description of the conditions under whichthe noise measurement was made.
(F) If the test conditions appear to have beenrepresentative of typical working conditions(for example, machines are installed in rever-berant surroundings, have suffered some wearand tear and are run fully loaded), no adjust-ment is necessary.
(G) If the test conditions are not representative (forexample, the test machine is in new conditionand is run on less than full load in non-rever-berant surroundings) add a 6 dB(A) correctionto the value in Box 2 and enter the result inBox 3.
If the test conditions are partially, but not fully,representative of your working conditions,select an appropriate correction between 0 and6 dB(A).
MODULE 8: 17
(H) The value in Box 3 is the estimated noise levelthe machine will introduce into the area inwhich it is installed. Remember that this valueis an estimate and that variations of ± 5 dB(A)are possible.
(I) The noise introduced by the new machine willcombine with the noise already present in thearea. To calculate the new noise level in thearea, enter the present noise level in theinstallation area in Box 4, then use the “AddingDecibels Table” to combine the levels in Boxes3 and 4.
For example. if a machine with a noise level of 78 dB(A)is introduced into an area where the existing noise levelis 80 dB(A), by using the “Adding Decibels Table” thenew noise level in the area will be 82 dB(A).
What if the supplier is unable to provide noiseinformation?
It may be possible to arrange for noise measurements tobe made of the same model of machine already installedelsewhere or of a machine set up in the suppliersworkshop. The supplier may be prepared to meet or atleast share the cost of having the measurements madesince the information would be useful in relation tofuture product promotion and sales.
How much weight should be given to noise whenassessing competing products?
This will depend mainly on the magnitude of theorganisation’s noise problem and the availability offunds.
As an example of a general policy on this issue, thepolicy of federal government agencies in the USA is topurchase noise-suppressed items automatically if theirprice is no more than 25 per cent greater than the priceof the cheapest otherwise acceptable item. If the priceis more than 25 per cent greater, purchase of the noise-suppressed item may still go ahead but is subject tojustification.
6. LACK OF
SUPPLIER
INFORMATION
7. PRIORITY FOR
NOISE
MODULE 8: 18
Representative:• Some machine wear and tear• Full load• Medium to high reverberation environment
Not representative:• New machine• light to medium load• Low reverberation environment
Were supplier's test conditions representative of typical working conditions and environment?
Sound pressure level Sound power level
No adjustment Subtract 8 dB(A)
_______ dB(A)
_______ dB(A)
_______ dB(A)
_______ dB(A)
_______ dB(A)
Result of supplier's noise measurement
Is the dB(A) value in box 1 a sound pressure level at the operator's position (typically 1 metre) or a sound power level?
No adjustment Add 6 dB(A)
Combine the values in boxes 3 and 4 using the adjacent "Adding Decibels" table
Adding Decibels
Add to higher level:3 dB2 dB1 dB0 dB
If levels differ by:
0 - 1 dB2 - 3 dB4 - 9 dB10 dB or more
Box 1
Box 2
Box 3
Box 4
Box 5
I
H
GF
E
DC
B
A
Estimated noise level the machine will introduce into the installation area
Present noise level in installation area
Estimated noise level in area following istallation
Estimated noise level at operator's position
(at 1 metre)
FLOW CHART 3: ESTIMATING THEAMOUNT OF NOISE A GIVEN MACHINEWILL INTRODUCE INTO THE WORKPLACE
MODULE 8: 19
What if no tender meets the noise specification?
As a matter of policy, plant which fails to meet the noisespecification should be accepted only with the writtenapproval of a senior manager who should check that:
• efforts have been made to locate alternative suppli-ers;
• negotiations have been held with tenderers todetermine the feasibility of additional noise controlwork on their products and the availability of noise-reducing accessories;
• the equipment is to be supplied with the maximumaffordable amount of noise reduction treatment inorder to minimise noise emission in the workplace;
• consideration has been given to the design of thearea in which the new equipment is to be installedto ensure that operator exposure levels will be aslow as workable.
Bruce, R.D. and Toothman, E.H., “EngineeringControls”, in Berger, EH et al. (Eds), Noise and HearingConservation Manual, 4th edition, American IndustrialHygiene Association, Ohio, 1986.
Middleton, A., “How to specify quieter machinery”,Works Management, vol. 37, no. 1, pp. 28-9,1984.
Pinder, J.N., “Noise specifications for industrial plantand equipment - avoiding shortcomings”, Noise andVibration Control Worldwide, pp. 292-5, October, 1982.
Bruel and Kjaer Ltd, Noise Control - Principles andPractice, Bruel and Kjaer Ltd, Denmark, 1986. (Text onpages 20-5 “Noise control of new projects” is especiallyuseful). This publication is available from ReidTechnology Ltd, PO Box 1898, Auckland.
8. FAILURE TO
MEET NOISE
SPECIFICATIONS
FURTHER
READING
MODULE 9: 1
MODULE 9: EVALUATING OPTIONS
Noise managerProduction/engineering staff.
To outline a method for assigning priorities to noisecontrol treatments on the basis of cost-effectiveness.
The relevant manager(s) should be able to:
• identify which machines or tasks contribute mostto the overall noise exposure of operators;
• estimate how much noise reduction is required;
• compare the effectiveness and cost of varioustreatment options;
• select the most cost-effective treatment, takingaccount of significant non-noise factors such asother health and safety considerations and produc-tivity.
IDENTIFYING NOISE CONTROL OPTIONS
ESTIMATING THE EFFECTIVENESS OF OPTIONS
SELECTING THE MOST EFFECTIVE TREATMENTOPTION
COSTING THE OPTIONS
EXAMPLE: STAMPING NUMBERS ON STEEL GASCYLINDERS
IMPLEMENTING THE CHOSEN SOLUTION
BASIC NOISE CONTROL
FURTHER READING
THIS MODULE
IS FOR
PURPOSE
OUTCOMES
CONTENTS
MODULE 9: 2
EVALUATING NOISE CONTROL OPTIONS
A walk-through audit of your workplace (as pointed outin Module 2: Walk-through Audit) is a good source ofideas for practical noise control options.
Noise measurements taken in the course of a moreformal noise survey are also a useful source of ideas fornoise control. As shown below, such measurementsalso enable the likely effectiveness of various options tobe estimated.
The most basic information to start with is a list of thetasks which each operator works, the associated noiselevels and how long each operator spends at each taskduring a typical working day. For a single operator, thisinformation can be summarised in a simple table:
Task number Noise level dB(A) Duration (Hours)
1 84 42 89 34 88 1
By using the Table 3 in Appendix 2 of the Core, the datain Table 1 above can be used to calculate the PartialNoise Exposure (PNE) associated with each task:
Task Noise level dB(A) Duration (Hours) PNE (Pa2h)
1 84 4 0.42 89 3 0.954 88 1 0.25
TOTAL 8 1.6
The sum of the PNEs for the 8 hours of the working dayis the Daily Noise Exposure (DNE), which in this case is1.6 Pa2h.
The above procedure — listing tasks and the amount oftime spent on them in a typical workday, then using thePascal-squared conversion table to calculate PNEs —can be repeated for each employee. The data for all theemployees in a given area can then be put together in a
IDENTIFYING
NOISE
CONTROL
OPTIONS
TABLE 1: BASIC
NOISE EXPOSURE
DATA FOR A
SINGLE OPERATOR
TABLE 2:
CALCULATION OF
PNEs FROM
NOISE LEVEL AND
EXPOSURE
DURATION
MODULE 9: 3
summary table. The following example shows partialnoise exposures (PNEs) for seven operators, each ofwhom works on one or more of the five tasks in anindividual pattern. The data could be for a smallestablishment or a section of a larger one.
Task Noise Totallevel Partial Noise Exposure of operator(Pa2h) for(dB(A)) A B C D E F G task
1 84 0.40 0.50 0.30 0.10 1.302 89 0.95 0.95 1.903 86 0.48 0.32 0.64 1.444 88 0.25 1.01 1.76 1.26 4.285 83 0.24 0.64 0.88
TOTAL (DNE)1.60 0.98 1.57 1.65 1.86 1.50 0.64 9.80
The sum of the PNEs in each column is the daily noiseexposure (DNE) for the operator concerned. Operator Ghas the lowest DNE (0.64 Pa2h) and operator E thehighest (1.86 Pa2h).
The sum of the PNEs in each row indicates thecontribution made to the total exposure by theassociated task. Note that task 4 contributes most tothe total exposure, even though task 2 has a higherdB(A) level.
It can be seen from this summary table that:
• noise exposure reductions are clearly necessary,since five of the seven operators are exposed toDNEs above 1.0 Pa2h (the current legal limit,equivalent to a noise exposure level (L
Aeq,8h) of 85
dB(A);
• task 4 is the major single contributor (4.28 Pa2h) tothe total noise exposure;
• task 4 is responsible for 3 operators (D, E and F)exceeding the exposure limit.
On this analysis, reducing the 88 dB(A) noise levelassociated with task 4 presents itself as an obvious noisereduction option to consider.
TABLE 3: PARTIAL
NOISE
EXPOSURES FOR
SEVEN
OPERATORS
SHARING FIVE
TASKS
MODULE 9: 4
To get some feel for the effectiveness of this option, wecan ask what would happen if the noise level of task 4was reduced by, say, 10 dB(A)? A reduction of 10 dB(A)is easy to work with because it means that eachassociated exposure would be reduced to one tenth of itsexisting value. However, it is not difficult to considerthe effect of any desired reduction, as shown later.
To continue with the present example, if the noise levelof task 4 is reduced by 10 dB(A) to 78 dB(A), eachexposure for task 4 is reduced to a tenth of its presentvalue and the table looks like this:
Noise Partial Noise Exposure of operator (Pa2h)level Total for
Task (dB(A)) A B C D E F G task
1 84 0.40 0.50 0.30 0.10 1.302 89 0.95 0.95 1.903 86 0.48 0.32 0.64 1.444 78 0.03 0.10 0.18 0.13 0.445 83 0.24 0.64 0.88
TOTAL (DNE)1.38 0.98 1.57 0.74 0.28 0.37 0.64 5.96
The main result is that the number of operators exposedto exposures above 1.0 Pa2h has dropped from five (withoperator B marginal) to two (with operator B marginal).
Task 2 now emerges as the highest contributor to thetotal exposure and to the individual exposures receivedby operators A and C, indicating that treatment of thenoise source for task 2, as well as the noise source fortask 4, may bring all operators below the currentmaximum permissible DNE of 1.0 Pa2h.
As before, we can estimate the effectiveness of thisadditional reduction by recalculating exposures on theassumption that the noise level associated with task 2,as well as that of task 4, has been reduced by 10 dB(A).This leads to the following table, in which the exposuresassociated with both tasks 2 and 4 have been reduced toa tenth of their original values.
ESTIMATING
THE
EFFECTIVENESS
OF OPTIONS
TABLE 4:
ESTIMATING THE
EFFECTIVENESS
OF A 10 DB(A)
REDUCTION OF
TASK 4
MODULE 9: 5
Noise TotalLevel Partial Noise Exposure of operator (Pa2h) for
Task (dB(A)) A B C D E F G task
1 84 0.40 0.50 0.30 0.10 1.302 79 0.10 0.10 0. 203 86 0.48 0.32 0.64 1.444 78 0.03 0.10 0.18 0.13 0.445 83 0.24 0.64 0.88
TOTAL (DNE) 0.53 0.98 0.72 0.74 0.28 0.37 0.64 4.26
The combined effect of both reductions is that alloperators are now exposed to DNEs less than 1.0 Pa2h(though the DNE for operator B remains marginal), andare therefore below the current legal exposure limit.
The approach outlined above may be used to estimatethe effects of various noise reduction treatments andcombinations of such treatments. While reductions of10 dB(A) in source noise levels have been used forconvenience in the above examples, it is of coursepossible to consider other values of reduction. Using acalculator, the following table of exposure reductionfactors may be applied directly to the PNE values inTable 3 above.
If noise level is reduced Divide the originalby the following number PNE or DNE byof decibels (dB(A))
1 1.32 1.63 2.04 2.55 3.26 4.07 5.08 6.39 8.010 101l 1312 1613 2014 2515 3216 4017 5018 6319 8020 100
TABLE 5:
ESTIMATING THE
EFFECTIVENESS
OF A 10 DB(A)
REDUCTION OF
TASKS 2 AND 4
TABLE 6:
EXPOSURE
REDUCTION
FACTORS
MODULE 9: 6
To consider the effect of a noise level reduction of 5dB(A) rather than 10 dB(A), the associated exposureswould be divided by 3.2 rather than 10.
In conjunction with a task-by-operator table of PNEvalues of the kind we began with (Table 3), Table 6 canbe used to estimate the individual and overall effects ofany proposed reduction in noise levels.
By exploring such options in advance, it is possible toget an overall “feel” for the machines or processeswhere a given noise level reduction will have the biggesteffects and, conversely, to avoid spending money ontreatments that will have only a limited effect. As anexample of the latter, a 10 dB(A) reduction in the noiselevel of task 1 in our original example would leaveunchanged the number of operators exposed above thepermissible limit. Again, it can be seen that the benefitof reducing the noise level of task 2 is fully realised onlyif task 4 is dealt with first.
In practice, it often happens that an operator’s exposureis determined by the noise of several machines runningtogether, so reducing the noise of a particular machinemay or may not result in as large a reduction of thenoise level at the operator’s position. One way to findout is to measure the noise level at the operator’sposition and note the reduction when the machine inquestion is switched off. Consultants use this techniqueto determine the dominant sources of noise at eachoperator’s position, systematically turning machines onand off and noting the effects. If machines cannot beswitched off for production or other reasons,consultants have special noise measurement techniquesthat take longer but enable the contribution ofindividual machines to be determined even when theyare all running at once.
As a further example of the use of Table 6, consider anentirely different approach, that is a uniform reductionof all noise levels by a relatively small amount, say 3dB(A). An overall noise reduction of this magnitude issometimes achievable by means of sound-absorptivetreatments to walls and ceilings.
A uniform reduction in noise levels of 3 dB(A) in Table 3would have the effect of halving all exposures (Table 6),
WARNING
MODULE 9: 7
producing the following result shown in Table 7.
It can be seen that an across-the-board reduction of 3dB(A) would bring all operators below the DNE 1.0 Pa2hlimit. On paper at least, this approach has roughly thesame effect as reducing the noise levels of tasks 2 and 4by 10 dB(A).
Noise Total Level Partial Noise Exposure of operator (Pa2h) for
Task (dB(A)) A B C D E F G task
1 81 0.20 0.25 0.15 0.05 0.652 86 0.48 0.48 0 963 83 0.24 0.16 0.32 0.724 85 0.13 0.50 0.88 0.63 2.145 80 0.12 0.32 0.44
TOTAL (DNE) 0.81 0.49 0.79 0.82 0.93 0.75 0.32 4.91
Another word of warning is in order here. Acousticalabsorption is an expensive treatment that may notchange sound levels close to machinery, exactly wheremany operators are required to work. It shouldcertainly not be applied without first seeking advicefrom an acoustics expert.
For illustrative purposes, however, let us suppose thatan acoustical consultant has confirmed that absorptivetreatment of walls and ceiling is a feasible option in theexample we are considering. The three treatmentoptions we have examined can now be ranked as followsin terms of relative effectiveness and contrasted withexisting conditions.
No. ofTotal Operators
Exposure whoseConditions (Pa2h) DNE ≥ 1 Pa2h
Existing conditions 9.80 7Option 1- reduce noise level of source4 by 10 dB(A) 5.96 2Option 2 - reduce noise levels of sources4 and 2 by 10 dB(A) 4.26 0Option 3 - absorption treatment to wallsand ceilings 4.91 0
TABLE 7:
ESTIMATING THE
EFFECTIVENESS OF
A 3 DB(A)
REDUCTION IN ALL
NOISE LEVELS
WARNING
TABLE 8:
COMPARISON OF
NOISE CONTROL
OPTIONS WITH
EXISTING
CONDITIONS
SELECTING
THE MOST
EFFECTIVE
TREATMENT
OPTION
MODULE 9: 8
On this analysis, options 2 and 3 would be equallyacceptable. Although they are quite differentapproaches they are about equally effective, in that eachwould roughly halve the total exposure and ensure thatno operator would be exposed above the legal limit.
Having determined the relative effectiveness of variousoptions, the next step is to cost them.
The first step in the costing process is to consider howthe required noise reductions can actually be broughtabout. A short list of basic noise control techniques islisted at the end of this module, together withreferences to some useful publications.
Acoustical treatment of the workplace, which includesinstalling screens and barriers, applying sound-absorbing treatment to surfaces such as walls andceilings, and enclosing machines operators, should bediscussed with a consultant or contractor beforeproceeding, especially concerning possible limits totheir effectiveness in your particular workplace. Theconsultant or contractor should be able to provide costestimates at the same time. As noted above, treatmentgenerally provides low reductions in noise level for allemployees. On the other hand, it involves littledisruption or machine down-time and has theadvantage of improving the acoustical comfort of theenvironment by reducing reverberation.
Treatment of the noise source usually results in largernoise level reductions than acoustical treatment of theworkplace itself, though at potentially greater cost interms of machine down-time and interference withproduction (unless modifications can be carried outduring scheduled maintenance down-time or outsidenormal operating hours). Source treatment presentsthree main sub-options, that is, substitution,modification or replacement.
COSTING THE
OPTIONS
ACOUSTICAL
TREATMENT OF
THE WORKPLACE
TREATMENT OF
THE NOISE
SOURCE
MODULE 9: 9
Substitution
Ideas for substitution can be gained from industryjournals and advice from equipment designers andmanufacturers, relevant industry associations orgovernment departments.
Modifications
For modifications, refer to the supplier of themachinery or equipment concerned because they mayknow of successful solutions already developed. Noisecontrol options are becoming more common on newequipment as the demand for quieter equipment grows.
Replacement
Replacement of an existing machine with a quieter onethat does the same job involves seeking informationfrom equipment suppliers, industry and tradeassociations and relevant government departments. Foradvice on how to request noise information and specifynoise limits when purchasing equipment, see Module 8:Buy Quiet.
The following example gives an overview of the mainfactors to be considered when comparing alternativesolutions to a given noise problem.
In a factory manufacturing steel gas cylinders, eachcylinder was numbered by an operator using a hammerand a set of number punches. The empty cylinder rangloudly at each hammer blow, causing the operators’noise exposure to exceed the permissible limit andplacing their hearing at risk.
The following noise control options were considered:
• Substituting a different process, that is, to “hand-write” numbers with an arc welder instead ofstamping them.
• Modifying the existing machine or process so thatbefore stamping, the cylinder was placed on a toughsound-absorbing mat and draped with a flexibleacoustical damping sheet.
• Replacing the existing machine with a quieter oneby using a hydraulic press to impress the numbersslowly under high pressure.
EXAMPLE:
STAMPING
NUMBERS ON
STEEL GAS
CYLINDERS
MODULE 9: 10
Table 9 lists the main factors taken into account inevaluating the three options. The replacement optionwas chosen.
Substitution Modification Replacement
Noise “hand-write” numbers place cylinder on replace manualControl with arc welder rope mat; drape stamping withOptions instead of stamping with lead-vinyl hydraulic press
damping sheetbefore stamping
Effects:• Noise moderate reduction moderate reduction substantial reduction
• Productivity mod. reduction slight reduction substantial increase• Health/ safety fumes, visual hazard unchanged unchanged
• Cost low low moderate
Unless your organisation has in-house expertise orprevious relevant experience, it is wise to get expertadvice on the feasibility, likely effectiveness andestimated costs of any noise solution you areconsidering, especially if significant expense is involved.
However, systematic analysis of various options alongthe lines mentioned above will have put you in aposition to work with a consultant most effectively. Youwill be able to discuss your organisation’s noiseproblems intelligently and make an informed appraisalof the consultant’s or contractor’s recommendations.
This is basically a matter of deciding whether to hire acontractor or to use your organisation’s resources. Thedecision depends on how specialised the job is and onthe expertise and availability of the organisation’s staff.The major options are:
• design and install the noise control solution en-tirely in-house, a solution not recommended forcomplex problems;
• design a solution and have it checked by an expertbefore installing it yourself;
• hire an expert to design the solution, then install ityourself;
TABLE 9:
COMPARISON OF
COSTS AND
BENEFITS OF
OPTIONS FOR
REDUCING NOISE
OF NUMBER-
STAMPING
OPERATION
IMPLEMENTING
THE CHOSEN
SOLUTION
VALUE OF EXPERT
ADVICE
ARRANGING FOR
WORK TO BE
CARRIED OUT
MODULE 9: 11
• hire an expert to design the solution and have acontractor install it.
The timetable for introducing noise controls will bedetermined mainly by the availability of funds andwhether installation of noise controls can be integratedwith other planned changes such as equipmentupgrading, alterations to processes or movement to newpremises. Other factors, such as a health and safetyinspector’s improvement notice or complaints fromemployees, employee representatives or nearbyresidents, can also be important at times.
Planning for the introduction of noise controls shouldtherefore be integrated with the organisation’s overallproduction and financial planning, and considerationshould be given to including noise control as apermanent item in the organisation’s budget until noisehazards are eliminated. Remember, noise is estimatedto cost the “average” manufacturing enterprise over$17,000 a year.
The basic techniques for reducing noise at source areto:
• Substitute quieter processes, for example: compres-sion riveting for impact riveting, welding forriveting, or hydraulic pressing for impact forging.
• Substitute quieter machines, for example: pressesfor hammers, hydraulic presses for mechanicalpresses, belt drives for gears, nylon for metal gears,or conveyor belts for rollers.
• Reduce impacts, for example: minimise loose playin gears, cams or chains, apply tough rubber orplastics to impacting surfaces, or minimise heightof fall.
• Reduce vibration, for example: balance rotatingparts, mount vibrating items on resilient mount-ings, reduce area of vibrating surfaces, or coatvibrating surfaces with damping material.
• Reduce transmission of sound through structures,for example: mount large vibrating machines on
IMPLEMENTATION
TIMETABLE
BASIC NOISE
CONTROL
MODULE 9: 12
vibration isolators or separate foundations, or useflexible shaft couplings, hoses, pipe and duct con-nectors.
• Reduce noise produced by air or gas flows, forexample: prefer low-velocity large-diameter pipeand duct systems over high-velocity small-diametersystems, or fit silencers on intakes and exhausts orstreamline flows.
Bruce, R.D. and Toothman, E.H., “EngineeringControls”, in Berger, E.H. et al. (Eds.) Noise andHearing Conservation Manual, 4th Edition, AmericanIndustrial Hygiene Association, Ohio, 1986.
Bruel and Kjaer Ltd., Noise Control - Principles andPractice, Bruel and Kjaer Ltd, Denmark, 1986, availablefrom Reid Technology Ltd, PO Box 1898, Auckland.
Health and Safety Executive, 100 Practical Applicationsof Noise Reduction Methods, HMSO, London, 1983.
SHARE Solutions on Noise, available from VictorianDepartment of Labour, Level 22, Nauru House, 80Collins Street, MELBOURNE, VIC 3000, or the localbranch of Occupational Safety and Health.
FURTHER
READING
MODULE 10: 1
MODULE 10: FACT SHEETS
Chief executive officerProduction/engineering staffMaintenance staffNurse/medical staffPurchasing staffEmployee representativesOHS committee
The fact sheets are intended to raise awareness about:
• the effects of noise and the value of good hearing;
• noise and noise control;
• ways of reducing noise exposure;
• personal hearing protectors.
FACT SHEET 1: EFFECTS OF NOISE AND VALUE OFGOOD HEARING
FACT SHEET 2: QUESTIONS AND ANSWERS ONNOISE AND NOISE CONTROL
FACT SHEET 3: WAYS OF AVOIDING HEARINGDAMAGE
FACT SHEET 4: HEARING PROTECTORS
THIS MODULE
IS FOR
INTENDED
OUTCOMES
CONTENTS
MODULE 10: 2
FACT SHEET 1: EFFECTS OF NOISE ANDVALUE OF GOOD HEARING
You depend on your hearing:
• to communicate;
• to socialise;
• to learn;
• to keep in touch with the world around you;
• to be warned of impending danger;
• to be entertained;
• to enjoy music and the sounds of nature.
Taking care of your hearing makes sense.
Up to half a million New Zealanders work in noisy jobs.Noise is a leading cause of hearing loss in adults. Manyworkers in the State of Victoria in Australia have hadtheir hearing tested as part of a Victorian governmentprogramme.
Some key findings were:
• over 80,000 workers were found to have damagedhearing, with many more workers yet to be tested;
• in some factories, more than half the workers hadimpaired hearing.
Though there are no data available for the situation inNew Zealand, it is likely to be similar. The population ofNew Zealand (3.5 million) is about 80% of that of theState of Victoria (4.4 million).
Noise problems are not confined to large organisations.There are a large number of workers exposed toexcessive noise in small manufacturing enterprises.
Noise destroys delicate nerve cells in the inner ear thattransmit sound messages to the brain. The nerve cellsare replaced by scar tissue which does not respond tosound.
GOOD
HEARING IS
IMPORTANT
NOISE IN
NEW
ZEALAND
WORKPLACES
WHAT DOES
NOISE DO TO
THE EAR?
MODULE 10: 3
The damage is painless but is also permanent and thereis no cure. Hearing aids can be of some help but fall farshort of restoring normal hearing.
Noise-induced hearing loss (NIHL) does not result intotal deafness. Those parts of the ear which processhigh-frequency sound are more affected than otherparts of the ear. The ability to hear low-frequencysounds can remain almost normal. This partial hearingloss can have a number of strange effects, including thefollowing:
• In quiet surroundings, such as the countryside, youmay hear far away thunder or a distant car (bothfaint low-frequency sounds) as well as anyone else.At the same time, you may fail to hear closersounds which are clearly audible to others, such asthe song of a bird or a cicada or the rustle of a smallanimal in the grass (faint high-frequency sounds).Such apparent inconsistencies in your behaviourcan make people think you are a dreamer or thatyou sometimes just pretend not to hear.
• Inconsistencies may also occur when listening tospeech. The loudness of speech is determined by itslow-frequency content, so it sounds as loud to aperson with NIHL as it does to most people; on theother hand the intelligibility of speech is deter-mined by its high-frequency content. To a personwith NIHL, many words sound the same and speechsounds jumbled. The typical complaints of a personwith NIHL are, “Don’t shout, I’m not deaf” and, “Ican hear but I can’t understand”. It’s easy to seewhy someone unaware of the nature of NIHL canmistake this hearing difficulty for low intelligenceand misinterpret requests to repeat what is said as adeliberate tactic to annoy or make conversationdifficult.
If your hearing is impaired it can affect many areas ofyour life.
Talking with people
If you have NIHL, everyone seems to mumble, so it is
HOW DOES
INNER EAR
DAMAGE
AFFECT
HEARING?
EFFECTS OF
HEARING
IMPAIRMENT
MODULE 10: 4
hard to have relaxed conversations, use the telephone,deal with people in shops and follow what’s going on atmeetings.
Social life
You may find yourself avoiding people because you areembarrassed about not being able to hear properly.Your family and social life may suffer. At work, you maybe passed over for promotion.
Quality of life
Being hard of hearing takes pleasure away from thingslike music, television, films and the sounds of nature.
Ringing in the ears
As well as impaired hearing, you may also suffer from“ringing in the ears”. This can be very distressing,especially if you are trying to sleep.
Safety/emergencies
If you have NIHL, you don’t always hear what’s going onaround you. You could miss a warning sound or a cryfor help, or misunderstand an important message. Inan emergency you could be a danger to yourself orothers.
Because enemy troops are usually detected by thesounds they make, the US Army studied the effects ofhearing loss on enemy troop detection.
They found that a sentry with normal hearing wouldhave almost two minutes warning of an approachingenemy soldier walking on leaves.
A sentry with poor hearing — about the same asmoderate industrial deafness — would not hear theapproach until the enemy was five steps away.
The same sentry with an additional temporary hearingloss, such as could be experienced after a day’s work in anoisy factory, would not hear the enemy approach atall.
Noise exposure which is high enough to causepermanent damage will usually cause temporary
WARNING
SOUNDS
OTHER EFFECTS
OF NOISE
MODULE 10: 5
hearing problems by the end of the working day.Hearing may be poor for some hours after work just atthe time when it is needed for relaxing with family orfriends, enjoying television or participating in otherleisure activities. Hearing will usually recoverovernight but if noise exposure continues, less and lessrecovery occurs and the temporary changes graduallybecome permanent.
Noise can be a safety hazard. It can distract attention,drown out the sound of a malfunctioning machine, analarm signal, a warning shout or a cry for help. Manypeople find high workplace noise levels irritating andstressful. Communicating in noisy areas requires extraeffort and concentration and there is a risk thatmessages or instructions will be misunderstood, leadingto mistakes, frustration and possible safety problems.
MODULE 10: 6
It is often incorrectly said that hearing loss is not as badas losing a finger or being injured in an accident.
Many hearing impaired people would gladly trade afinger to have normal hearing again.
Recent research at the University of Montreal highlightsa number of consequences of noise-induced hearingloss (Hetu R., Riverin L., Lalande L., Getty C. and St CyrC. “Qualitative analysis of the handicap associated withoccupational hearing loss”, British Journal ofAudiology, vol. 22, pp. 251-64, 1988). The research,which was based on reports from industrial workers,revealed that workers have to expend extra effort toovercome their hearing loss, suffer from anxiety, stressand fatigue and feel isolated in groups.
Extra effort is required by the workers because:
• they must be more attentive in communicatingwith others;
• they must concentrate more in conversations;
• it is annoying to ask others to repeat themselves;
• adjustments demand a great deal of effort.
Anxiety and stress were caused because:
• noise at home is bothersome;
• ringing in the ears is very annoying;
• workers worry about the condition of their hearingand the noise level at work;
• noise at work led to aggressive behaviour; and
• of the inability to hear the telephone ringing.
Workers reported that:
• after work it is very annoying to feel the sensationthat their ears are blocked;
EFFORTS
ANXIETY AND
STRESS
FATIGUE
FACT SHEET 2: QUESTIONS AND ANSWERSON NOISE AND NOISE CONTROL
WHAT’S A BIT
OF HEARING
LOSS
MODULE 10: 7
• they have headaches;
• they need peace and quiet;
• they feel too tired for normal activities.
Workers said that their hearing problems had led tochanges in their social activities because:
• they are less communicative in groups;
• they are more and more isolated in groups;
• they participate less and less in group discussions;
• their inability to follow group discussions is annoy-ing.
Therefore the real question is, “If it’s entirelypreventable, what’s the point of having the ears of a 70-year-old when you’re only 20?”
“I’m young, I’ll worry about it later. It’s mostly theolder ones who are hard of hearing”, is sometimes said.
However, most older workers with noise-inducedhearing loss have had it since they were young. Thereason it is more noticeable among older workers isthat the additional hearing loss that comes with agemakes it impossible for them to hide their difficulties.
The time to prevent noise-induced hearing loss is fromthe first day in a noisy environment. You may havethought, “I’ll notice if noise is affecting my hearing andI’ll do something about it then”.
Unfortunately, however, you probably won’t notice.Noise-induced hearing loss develops gradually over aperiod of months to years, depending on the degree ofexposure. The process is slow and painless and very fewpeople notice it happening until quite a lot of hearinghas been lost.
There is no cure for noise-induced hearing loss, so allyou will be able to do is learn how to live with apermanent hearing impairment.
EFFECTS ON
GROUP ACTIVITIES
I’M YOUNG,
WHAT DOES
IT MATTER?
MODULE 10: 8
The two main aspects of noise which determine whetherit is harmful are:
• how loud the noise is;
• how long you are exposed to it each day.
Noise starts to be a risk to hearing when it is about asloud as heavy city traffic, that is about 85 decibels (85dB(A)). You can work all day in noise levels below 85decibels with little risk of hearing damage.
Above 85 decibels, the risk increases rapidly as the noisegets louder. At 100 decibels, for example, exposureshould be no more than 15 minutes a day.
Although the best way of judging if a noise is harmful isfor a trained person to measure it, there are also somesimple indicators. Some of the indicators that a noise islikely to be harmful are:
• the noise is as loud or louder than heavy city traffic;
• you have to raise your voice to speak to someone ametre away;
• people who have worked in the noise for a whileseem to be a bit deaf;
• things sound different after exposure to the noise;
• you hear ringing or other noises in your ears afterexposure to the noise;
• you often have to strain to catch what people aresaying;
• you have to turn the radio or TV higher than youused to;
• members of your family say you seem to be havingproblems with your hearing.
Yes, it certainly can. One exposure is unlikely to causepermanent harm, although you may notice sometemporary effects like muffled hearing. However, therisk of permanent hearing damage increases:
• the more often you are exposed;
• the louder the music;
• if you have already been exposed to loud noise thatday, for example in a noisy job.
WHAT MAKES
A NOISE
HARMFUL?
CAN LOUD
MUSIC HARM
MY HEARING?
MODULE 10: 9
The safe way to listen to your favourite music is to:
• alternate between loud and quiet music;
• give your ears a complete rest for ten minutes everyhalf hour;
• be alert for effects such as ringing in your ears ormuffled hearing.
If you experience such effects, take them as a warningthat you are over-loading your ears and change yourlistening habits. Be particularly careful if you work in anoisy job, because noise exposures add up.
An employer has said, “Why should I have to worryabout the noise in my factory when young people can goto a disco after work and blast their ears off?”
Our ears are able to cope with exposure to loud noiseprovided it doesn’t last too long and is not repeated toooften.
Although disco and other amplified music can be veryloud, exposures are typically brief and infrequentcompared with exposures at work. Therefore, much lesshearing damage is caused.
In a survey of over a thousand young people in Sydney,many of whom had often attended concerts and discos,researchers from the National Acoustic Laboratories(the Commonwealth Government scientific laboratorythat specialises in the study of noise and hearing) failedto find any clear cases of music-induced hearing loss.(Carter N., Waugh R., Keen K., Murray N. and BulteauV., “Amplified music and young people’s hearing”,Medical Journal of Australia, vol. 2, pp. 125-8, August 7,1982.)
This is not to say that no one has ever suffered hearingdamage as a result of loud music, but it does indicatethat significant damage is rare. By contrast, there arenow about 9,000 cases of occupational hearing lossevery year in New Zealand.
Another point to bear in mind is that employers areunder a legal obligation to control noise exposure in theworkplace. Government takes the view that, just as theexistence of non-occupational risks of injury does not
EMPLOYER:
WHY SHOULD
I HAVE TO
WORRY?
MODULE 10: 10
relieve employers of the responsibility to guarddangerous machines, the existence of non-occupationalnoise hazards does not relieve employers of theresponsibility to control noise hazards in the workplace.
It is often assumed that noise control is very expensiveand that in most cases it is probably impossible to doanything about the noise anyway.
It’s true that some noise controls are expensive,especially if equipment has to be modified afterinstallation. This is why it makes sense to buy quiet.Even if it is more expensive, it is better to buy quietequipment at the outset than to make costlymodifications later.
To help break down the myth that noise control workalways costs a fortune, consider the following examplesof really inexpensive noise solutions:
• A noise consulting firm achieved a 50 decibelreduction (that’s a lot) in the noise made by cycloneseparators by inserting a small metal plate thatbroke up a resonant airflow that was causing ahigh-pitched whistle. The cost was $1 per machine.
• After advice from a noise consultant, one of themaintenance staff of a small company built sound-proof enclosures around several noisy machines.The machine operators helped with the design toensure that access and production were notaffected. The enclosures were made of plywood andceiling insulation material enclosed in plasticgarbage bags and chicken wire. The material costwas about $440 per enclosure. The enclosures wereeffective and removed the need for the operators towear hearing protectors.
• A French company has developed an “intelligent”rock breaker that senses the nature of the rock andthen adjusts the strength and direction of theimpacts to break it up as efficiently as possible.Operation is claimed to be virtually vibration-free,with no overheating and little noise.
A lot of noise control work is neither expensive norcomplicated once some basic principles are understood.An excellent guide to noise control principles, written
ISN’T NOISE
CONTROL
EXPENSIVE?
MODULE 10: 11
in simple language and clearly illustrated, is nowavailable from Bruel and Kjaer. Details are at the end ofthis fact sheet.
Another useful publication (also listed at the end) is 100Practical Applications of Noise Reduction Methods,from which the following examples are drawn. Theyshow noise levels at the operator’s position of variousmachines before and after simple, inexpensivetreatments. In most cases, the noise level has beenreduced to the point where the operator would not needto wear hearing protectors.
Problem Noise Control Noise level CostMachine (dB(A)) ($)
Before After
paper reeler replace steel with 99 86 825with bronze gears
paper cutter replace steel with 93 85 275plastic gear
plastic grinder redesign feed hopper 95 83 110
book binder line case guard 95 85 45with polyurethane
grinder replace steel with 92 82 50%plastic chute less
band saw enclose in acoustic 101 91 2,500curtains
The expense of noise control work has to be weighedagainst the existing costs of noise. Module 6: Costs/Benefits explores this question and concludes thatuntreated noise costs the average manufacturingenterprise over $17,000 per year, to say nothing of theeffects on the employees’ hearing and health.
Inexpensive noise controls like those listed above are aprofitable investment for an organisation and they havevery positive health, safety and comfort benefits foremployees.
Bruel and Kjaer Ltd., Noise Control - Principles andPractice, Bruel and Kjaer Ltd., Denmark 1986, availablefrom Reid Technology Ltd, PO Box 1898, Auckland.
Health and Safety Executive, 100 Practical Applications ofNoise Reduction Methods, HMSO, London, 1983.
PUBLICATIONS
MODULE 10: 12
FACT SHEET 3: WAYS OF AVOIDINGHEARING DAMAGE
The best way to avoid hearing damage is to cut downthe noise that people are exposed to. The main ways todo this are by:
Controlling the source of noise
A great deal of noise control is just common sense.Large noise reductions were made in one factory simplyby lining metal chutes and bins with scrap conveyorbelting.
Stopping the noise from reaching people
This may be done by moving a noisy machine away frompeople, by building a soundproof enclosure around it orby putting up a barrier between the machine andpeople.
Reducing the time people are exposed
Quiet work, like packing or inspecting, should be donein a quiet place. Where possible, people should swapbetween noisy and quiet jobs so that nobody getsexposed for too long.
While it is up to the employer to approve such changes,employees may be able to contribute ideas and helpwith trialing changes. If you can see ways yourworkplace might be made quieter, suggest them to yoursupervisor, safety committee or employer.
If exposure is still excessive after all possible controlmeasures have been taken, individual protection isavailable from earmuffs or earplugs. Fact Sheet 4:Hearing Protectors has detailed information aboutpersonal hearing protectors.
Employees’ health and safety at work is protected bylaw. Employers have a duty to protect employees and tokeep them informed about health and safety matters.Employees have a responsibility to look afterthemselves.
Employers have a duty to keep noise exposure withinsafe limits. The preferred ways of doing this are to
HOW CAN
HEARING
DAMAGE BE
AVOIDED?
DUTIES AND
RESPONSIBILITIES
MODULE 10: 13
reduce the amount of noise made by plant andequipment and/or to reduce the amount of timeemployees are exposed to noise.
If these methods fail to reduce noise exposure below thelegally specified limits, the employer has a responsibilityto provide employees with suitable hearing protectorsand to provide adequate information and instruction intheir use.
Employees also have duties. They include:
• taking care of their own health and safety and thatof others who may be affected by what they do;
• using noise controls supplied with machinery orinstalled in the workplace;
• reporting damaged noise control equipment andhearing protectors for repair or replacement;
• using hearing protectors in declared noise areas.
Cooperation between managers and employees is likelyto produce the most cost-effective and mutuallysatisfactory solutions to noise problems in theworkplace.
Managers can contribute by:
• developing noise management policies, plans andpractices in consultation with workers;
• arranging for a full assessment to be made of noisyareas in the workplace;
• fully investigating engineering noise control op-tions;
• discussing control options with workers to ensureminimal adverse effects on ease of operation,maintenance access and productivity;
• seeking outside advice on noise control as neces-sary;
• specifying the lowest affordable noise limits whenpurchasing plant and equipment;
• signposting noisy areas and equipment;
• providing good quality graded hearing protectors;
• involving workers in the selection of hearing
COOPERATION
MODULE 10: 14
protectors and allowing them choice to ensure thatthey can obtain a suitable fit;
• always wearing hearing protectors themselves innoisy areas.
Employees can contribute by:
• taking a constructive interest in the workplace’snoise problems;
• helping to develop policies, plans and practices fordealing with workplace noise problems;
• suggesting possible noise controls for machinesthey operate;
• helping plant engineers or consultants designsolutions;
• using any noise control equipment supplied;
• taking responsibility for the preservation of theirown hearing by using hearing protectors wheneverthey are in the presence of hazardous noise.
MODULE 10: 15
FACT SHEET 4: HEARING PROTECTORS
If noise exposure at work can’t be made safe by limitingthe level of noise or the amount of time employees areexposed to it, employers have a responsibility to provideemployees with suitable hearing protectors andemployees have a responsibility to use them.
The main types of hearing protector are earmuffs andearplugs. Either type can provide effective protectionprovided it makes an airtight seal in your ear (plugs) oraround it (muffs).
Hearing protectors reduce sound to safe levels ratherthan block it out completely. A well-fitted hearingprotector will give at least the same noise reduction ascan be obtained by pressing the hands very firmly overthe ears (see Figure 1).
Figure 1: Well-fitted hearing protectors give at least the samenoise reduction as pressing your hands firmly against the ears
If you have never worn hearing protectors before, usethis method to find out what to expect from them:
• find a noisy place at work;
• block your ears firmly with the heels of your handsas shown in Figure 1;
• experiment with different positions of your handsand different pressures.
Your hearing protectors should give about the samenoise reduction as the best you can achieve with yourhands.
WHAT TO
EXPECT FROM
HEARING
PROTECTORS
INTRODUCTION
MODULE 10: 16
Always READ THE INSTRUCTIONS supplied with theear plugs.
Some earplugs, for example, the compressible foamtype, come in only one size. If the plugs are made inseveral sizes, you need the correct size for each ear.
To fit the left ear:
• Reach around your head with your right hand andtake hold of the back of your left ear about half waydown (see Figure 2).
• Gently pull your ear outwards and upwards tostraighten your ear canal.
• Insert the plug into your ear canal with your lefthand.
To fit the right ear:
• Reach around your head with your left hand andtake hold of the back of your right ear about halfway down.
• Gently pull your ear outwards and upwards tostraighten your ear canal.
• Insert the plug into your ear canal with your righthand.
Figure 2: The correct method for fitting ear plugs
If the plug is a compressible foam type:
• Roll the plug slowly and smoothly into a cylinderabout this round (4..5- 5 mm). Depending onhow small you roll the plug, it can take up to 30seconds to do this, possibly longer if you haven’tdone it before.
• Immediately insert the plug well into the ear canaland hold it in place until it has begun to expand
FITTING
EARPLUGS
MODULE 10: 17
and block the noise. Aim to get three-quarters ofthe length of the plug into the canal.
Points to remember are:
• Plugs can work loose and may need to be re-posi-tioned;
• Remove plugs slowly so that suction cannot hurtyour ear.
The following points will assist you to fit your earmuffs:
• Inspect the muffs and note which way they aremeant to be worn. Some earmuff cups are markedTOP or FRONT and should be worn that way. Oval-shaped cups are meant to be worn so that the ovalis vertical (NOT as in Figure 3).
Figure 3: Incorrect location of ear muff cups
• Extend the headband to its maximum length(Figure 4).
Figure 4: Extend headband to its maximum length
FITTING
EARMUFFS
MODULE 10: 18
• Brush as much hair as possible away from your ears(Figure 5).
Figure 5: Brush hair away from ears while fitting muffs
• Place the muffs over your ears, making sure thatthe ears fit right inside the cups (Figure 6).
Figure 6: Ears fit inside the earmuff cups
• Hold the cups firmly in place by pressing inwardsand upwards with your thumbs, then tighten theheadband so that it takes the weight of the cups andholds them firmly in position (Figure 7).
Figure 7: Tightening the headband to hold cups firmly inposition
MODULE 10: 19
• Now run your fingers around the cushions to checkthat they are making a good seal against your headeverywhere. Some things that can prevent a goodseal are prominent cheek bones, an unusually deepgroove behind the lower jaw, thick hair, a cap(Figure 8 left) and spectacle frames (Figure 8right).
Figures 8: Caps and spectacle frames can prevent a good seal
• If you are unable to get a good seal, try differentearmuffs, change your spectacle frames to a thinnertype or try earplugs instead.
To ensure your hearing protectors are hygienic andcontinue to provide adequate protection:
• Keep your earmuffs and earplugs clean with soapand water.
• Replace hard or damaged earplugs with a new pairimmediately.
• DON’T stretch the headband of your earmuffs. Itmakes them less effective.
• Replace the cushions on your earmuffs as soon asthey start to harden.
• Immediately replace worn or damaged parts ofearmuffs.
It takes two to three weeks to get used to wearinghearing protectors. Everyone finds them a bit strangeto start with, but once you are used to them you willappreciate their good points, that is:
LOOKING
AFTER YOUR
HEARING
PROTECTORS
GET USED TO
WEARING
HEARING
PROTECTORS
MODULE 10: 20
• You’ll feel less stressed while you’re working;
• You’ll feel less tired at the end of the day;
AND
• You’ll know your hearing is safe.
Is there any danger in putting earplugs in your ears?
Earplugs are soft and are not long enough to reach farinto the ear canal so it’s virtually impossible to doyourself any harm with them. However, if you have anear infection, or have ever had ear surgery, check with anurse or doctor before using earplugs.
What if I don’t wear hearing protectors all the time?
Taking protectors off even for short periods can canceltheir protective effect. To be fully protected, you needto wear protectors all the time you are exposed to loudnoise.
My hearing protectors feel uncomfortable.
Earmuffs and earplugs will probably feel awkward anduncomfortable when you first start to wear them.Usually these feelings vanish in about two weeks andyou really begin to appreciate the relative peace andquiet the protectors create. If you are having problems,speak to your supervisor or health and safetyrepresentative about trying different protectors.
If I wear hearing protectors, I won’t be able to hear mymachine properly.
Your machine will certainly sound different when youwear protection, but you should still be able to detectchanges in the noise it makes.
Is there any point in wearing hearing protectors if myhearing is already impaired?
Your ears will go on being damaged as long as they areexposed to excessive noise. The hearing you have left isvery precious. There certainly is a point in protectingit.
I won’t be able to hear what people are saying if I wearhearing protectors.
Actually, if your hearing is normal the opposite is true.You will find it easier to understand what people are
SOME
QUESTIONS
AND
COMPLAINTS
MODULE 10: 21
saying when you wear protectors because your ears areno longer overloaded. The effect is like wearingsunglasses, that is, you can see better when the glare iscut down. lf your hearing is already impaired, you maynot be able to understand speech better when you wearprotectors. Depending on the kind of impairment, youcould find it harder to understand speech.
If you have this problem, don’t give up the protectors.It’s important to protect your remaining hearing. Askpeople to speak up, or find another way to commun-icate. For example, use hand signals or a note pad.
What about noise exposures outside work?
This is an important question. Noise exposures add up,so you need to watch your noise exposure outside worktoo. Wear hearing protectors if you use power tools likesaws, grinders, motor mowers or chainsaws and limityour exposure to very loud music.
If you shoot, wear protectors if you fire anything louderthan a .22 rifle. Always wear hearing protectors onindoor firing ranges.
Should I have my hearing checked?
Employers are required to provide regular free hearingchecks for their noise-exposed employees. If you areconcerned about your hearing, or would like to haveregular hearing checks but your employer doesn’t havea hearing check programme, ask your family doctor oryour local branch of the Occupational Safety and HealthService of the Department of Labour for advice.
MODULE 11: 1
INFORMATION
Noise managerTraining coordinator.
This module is designed to assist the noise managergain the support, commitment and participationnecessary for an effective noise managementprogramme from the following key groups:
• senior managers;
• production managers, engineers and technicians;and
• employees and supervisors.
INTRODUCTION
SENIOR MANAGERS
PRODUCTION MANAGERS, ENGINEERS ANDTECHNICIANS
EMPLOYEES AND SUPERVISORS
SESSION 1: NOISE, A MAJOR ISSUE
SESSION 2: NOISE, AN ISSUE IN THISORGANISATION
SESSION 3: IDENTIFYING AND SOLVING NOISEPROBLEMS
SESSION 4: THE EFFECTIVE USE OF PERSONALHEARING PROTECTION
EVALUATION
MODULE 11: TRAINING AND
THIS MODULE
IS FOR
PURPOSE
CONTENTS
MODULE 11: 2
TRAINING AND INFORMATION
A successful noise management programme requiresthe full support, commitment and participation ofmanagers, engineers and technicians as well asemployees and supervisors.
Each of these groups has a special role in ensuring thatnoise problems are eliminated from the organisation.They have special needs for information and mustunderstand how they can participate in the overallprogramme. This module provides advice and ideas forachieving effective communication and informationsharing with each group.
In addition, OSH’s Management of Noise at Work:Resource Kit contains resources which can assist thisprocess. These resources include a noise video(produced by Worksafe Australia), a multi-lingualcassette, fact sheets and a booklet with basicinformation about noise, posters and stickers to identifynoisy work areas or machines, and a copy of thepublication List of Graded Hearing Protectors.
A noise management programme will not get off theground without the financial, resource and personalsupport of senior managers. This module providessome ideas for achieving management support. It alsoincludes a format for a report to senior managementwhich would enable them to assess, approve and beinvolved in a noise management programme.
Achieve management commitment to and cooperationin a long-term programme to reduce noise and noiseexposure.
Inform managers about:
• their legal obligations;
• the human and economic costs of noise-inducedhearing loss and benefits of effective noise manage-ment;
• effective management of noise,
OBJECTIVE
SENIOR
MANAGERS
INTRODUCTION
MODULE 11: 3
Involve managers in:
• establishing effective policies and mechanisms forthe management of noise;
• preparing a forward plan for the control ofworkplace noise;
• implementing noise control measures.
The outline report Noise Management Proposal -Organisation “X”, which is included in this section,provides a handy framework to assist in the preparationof a report or presentation to senior managers or simplydocument your analysis of the problem and its possiblesolution. You will find details to assist completing sucha report in the Core and other modules of this controlguide.
As the initiator of the planning process to reduce noisein your organisation, you will need to design anapproach that will ensure that the programme is widelyaccepted and successfully implemented. Consultationand participation are critical ingredients of the process.
The exact nature of the development process willdepend on a range of factors including:
• your position/responsibility/authority in the organi-sation;
• the size and nature of your business;
• established reporting and consultative procedures;
• the organisational “climate” (for example, employeerepresentative /management relations and communi-cation networks);
• the source of impetus for the programme, forexample:
- a visit from a health and safety inspector;
- compensation claims for industrial deafness;
- awareness of senior management of the problemand its costs;
- the action and enthusiasm of an occupationalhealth and safety (OHS) practitioner (for example,an OHS nurse or hygienist);
- the undertaking of a noise survey.
DEVELOPING A
REPORT FOR
MANAGERS
MODULE 11: 4
Planning a noise management programme requirescareful research of the problem and its effects on yourorganisation.
To adequately address the points raised in the outline,you will need to discuss the problem with a range ofworkplace personnel and be well acquainted withspecific workplace problems. In larger organisations,such a report would ideally be prepared under the aegisof an OHS committee or an especially convenedcommittee representing the major interest groups. Aswell as ensuring access to the necessary information tocompile such a report, this process will foster broaderownership of the programme and facilitateimplementation.
Key groups to inform and involve are:
• supervisors and leading hands;
• employee representatives;
• engineering design and production managers andstaff;
• purchasing staff;
• maintenance staff,
• occupational health and safety and rehabilitationstaff;
• employees.
The level of involvement of each group will depend onthe size and nature of the organisation, but all shouldbe informed of the development of the noisemanagement programme.
Other steps you can take to ensure the successful designand implementation of the noise managementprogramme are:
• Address the major concerns relevant to the styleand climate of your organisation. For example, inan organisation with an ethos that highly values“looking after” its workforce, highlight the debili-tating effects of noise on the company’s employeesand in a cost-conscious organisation emphasise thecost or potential cost of noise.
• Involve influential personnel in the developmentprocess to maximise the programme’s credibilityand assist in the implementation phase.
MODULE 11: 5
• Involve your senior managers by accompanyingthem on a walk through areas to demonstrate andhighlight problems that exist on the shop floor.
• Generate an initial interest in the problem of noisebefore going too far with a detailed proposal (forexample, use promotional material such as factsheets and videos to generate interest).
• Establish an on-going, active role for senior manag-ers in the implementation of the programme by:
- providing regular progress reports on implementa-tion;
- involving them in presenting employee educationand briefing sessions to demonstrate managementcommitment and support;
- obtaining personal endorsement of policies andprogrammes;
- encouraging them to wear personal hearing protec-tors whenever they enter noisy work areas.
• Where possible in the report, use examples fromyour workplace to illustrate solutions and theirbenefits and costs.
Background (Core Step 1 plus Module 10)
What sort of a problem is noise? Include informationon:
• the effects of noise;
• how noise can be controlled.
What legislative requirements apply?
Situational Analysis (Core Step 2 plus Modules 1, 2,6)
How serious a problem is noise in this organisation?Include information on:
• existing noise exposures (noise levels and exposuredurations);
• current costs of noise;
• effects on organisation’s employees.
What is the organisation currently doing about noise?
SAMPLE NOISE
MANAGEMENT
REPORT
MODULE 11: 6
Include information on:
• the cost of existing measures;
• the effectiveness of existing measures;
• whether the organisation is complying with legisla-tion.
What are our competitors doing?
What is the attitude of employee representatives,employees, supervisors and managers to this problem?
Possible Action (Core Steps 3, 4, 5 plus Module 6)
What can this organisation do to improve its currentaction (options)?
What will the options cost?
What benefits will accrue?
What is the attitude (actual or expected) of key playersto this initiative (for example employee representatives/production managers/finance staff)?
Proposed Noise Management Strategy (Core Step 3, 4,5 plus Modules 3, 5, 11, 12)
(This section may not be presented in much detail untila noise survey is conducted and costs are estimated.)
Programme outline
Resource plan and budget
Implementation strategy
Evaluating the effectiveness of the programme
Recommendations
Agree to a tour of the problem areas
Agree to the proposed noise management strategy
Appendix A
Results of walk-through noise assessment (Modules 2,5)
Where noise is a major problem for an organisation, itwill be important to ensure that in-house expertise innoise control is available or built up over a period oftime. The effective use of consultants can assist withdeveloping and enhancing in-house expertise.
PRODUCTION
MANAGERS,
ENGINEERS
AND
TECHNICIANS
MODULE 11: 7
Material in the Core and other modules of this controlguide will assist competent engineers and techniciansdevelop and implement noise control measures.
Achieve cooperation, commitment and action to designand purchase quiet machinery.
Inform technical/production staff about:
• their legal responsibilities;
• the human and economic costs and benefits;
• the organisation’s policies and programmes.
Involve the technical/production staff in:
• controlling noise at source;
• implementing “buy quiet” policies;
• effective maintenance.
In addition, this group of employees will need toincrease their skill levels in producing engineeringcontrols of noise.
The remainder of this control guide containsinformation and further references to assist in theengineering control of noise. If your organisation has anumber of technical staff who design, commission andmaintain plant, a specific training exercise on noisecontrol may be required as a refresher or to put noisecontrol on their agenda.
The best approach is to demonstrate what otherorganisations have been able to achieve (see Module 1:Case Studies) and work through an actual workplacenoise problem. Module 2: Walk-through Audit, Module3: In-house Control and Module 9: Evaluating Options,provide an effective basis for problem analysis anddiscussion. If a comprehensive noise survey has beenundertaken, this could assist in deciding where tobegin.
It may be necessary to precede the case study with somegeneral information about the organisation’s noisemanagement policy and programme and the legislativecontext. Session 2 “Noise - An Issue in thisOrganisation”, which is outlined later in this module,provides an appropriate format.
OBJECTIVE
COMMUNICATING
WITH
PRODUCTION
MANAGERS,
ENGINEERS AND
TECHNICIANS
MODULE 11: 8
While the onus for maintaining a safe and healthyworkplace is a management responsibility, employeeshave a right to know the hazards they face and,particularly with appropriate training, can contribute totheir identification and control.
The involvement of supervisors and employees in noisecontrol becomes particularly important where thewearing of personal hearing protection is required. Inaddition, the workforce represents a considerable bodyof knowledge from which to draw information aboutnoise problems and their control. Employees are morelikely to cooperate in effectively using personal hearingprotection where they can see that the organisation hasa commitment to a long-term programme to reducenoise levels to safe limits and where their contributionsto the control of noise at source are being sought andused. Employees should also have a say in priority-setting through representatives on the noise oroccupational health and safety committees.
Achieve cooperation and participation of employees inthe reduction of noise and noise exposure.
Inform employees about:
• the hazard and its personal effects;
• methods of noise control and hearing protection;
• the organisation’s policy and programme to controlnoise;
• the relevant legislative requirements (that is,employees’ rights and obligations).
Involve employees in:
• identifying local noise problems;
• generating possible solutions to noise problems;
• ensuring proposed noise control solutions meetoperator requirements for access, control, comfortand productivity;
• the effective use of personal hearing protection.
WORKERS
AND
SUPERVISORS
OBJECTIVE
MODULE 11: 9
A proposed series of four sessions which could form thebasis of a comprehensive training programme foremployees, are outlined below. These outlines can beused in the following ways:
• An in-house person with good communicationskills can use them to obtain the detail necessary toprepare and conduct sessions.
• They can form the basis for briefing external con-sultants to present sessions.
• They can be used as a checklist to see whether yourexisting training programmes cover the informa-tion recommended for employees.
• They can be included in existing in-house trainingprogrammes (for example, induction or apprenticetraining).
Include representatives of the target groups in planningand implementing the training programme (forexample, through the OHS committee or a speciallydesignated group).
Planning
Assess the existing level of knowledge of your audience,their attitudes to noise and their interests, then directthe information accordingly.
Avoid relying heavily on one method of communicationalone. Use a combination of lecture sessions, writtenmaterials, audio-visuals, on-the-job training andposters.
Contact supervisors and production managers well inadvance of training to ensure the release of employeesto attend sessions.
Request that senior management directly supportsattendance of employees where sessions are conductedin normal working hours.
Content and presentation
Make information as directly related to the workplace aspossible through the use of local examples andactivities.
Draw on the expertise and the influential people, bothinside and outside the organisation, to deliver andsupport key information.
TRAINING
WORKERS AND
SUPERVISORS
MODULE 11: 10
Be aware of community literacy levels and provideinformation in community languages where required.A variety of services are available to assist in doing thisand materials such as multilingual audio-tapes are alsouseful for this purpose.
Use a participative approach which draws on and utilisesthe expertise and knowledge of the workforce through,for example, scheduling group discussions and tasks.
Be aware that there may be members of your workforcewho are already suffering the effects of noise-inducedhearing loss. This may be due to exposure to noise intheir job with your organisation, a previous job or non-occupational exposures. Ensure you are sensitive to thepossibility of emotional responses from sufferers and,prior to conducting these sessions, have a plan whichcan be explained at the first session for constructivelyassisting these employees.
NOTE:
MODULE 11: 11
SESSION 1:
NOISE A
MAJOR ISSUE
Purpose
To establish the relevance of noise as a workplaceproblem which can dramatically affect the quality oftheir lives.
Desirable Outcomes
I understand what noise can do to my family and me.
I want my exposure to noise to be safe.
I am prepared to talk about how noise currently affectsme.
I know what to do if I suspect that I am currentlysuffering from the symptoms of noise-induced hearingloss.
I am interested in learning what this organisation isdoing about noise in the workplace.
Contents
1. What it is like to have noise-induced hearing loss:
- explain and demonstrate the nature of thedisability;
- indicators of hearing loss or risk of hearing loss.
2. Basic physiology of the ear and the effects of noiseexposure:
- effects of noise intensity;
- exposure duration;
- effects such as tinnitus, stress and irritation.
3. How common is the problem:
- national statistical picture;
- organisation statistics, audiometry results (ifavailable) or anecdotal information;
- what industries and occupations are most at risk.
4. (GROUP DISCUSSION) The effects of this type ofdisability on:
- work activities;
- relationships with family and friends;
- recreation (for example, participation in sport,radio, TV and music);
- use of telephone;
MODULE 11: 12
- group activities (for example, parties, meetingsand conversations).
5. Access to advice/ counselling/ rehabilitation onnoise-induced hearing loss for employees:
- organisation rehabilitation adviser;
- staff counselling facilities.
Resources
The Noise Video and Fact Sheets in OSH’s NoiseManagement At Work - Training Resources.
MODULE 11: 13
Purpose
The purpose of this session is to:
• establish that noise is an important issue in thisorganisation;
• outline what is being done to manage the problem;
• outline employees’ roles in the process.
Desirable Outcomes
I understand what this organisation is doing aboutnoise and its motives for doing this.
I understand who is responsible (specifically) formanaging noise in this workplace and I know thepolicies and procedures that apply.
I understand how I can contribute and am prepared toparticipate in the management of this problem.
Contents
1. Noise management and the law:
- relevant sections of the Health and Safety inEmployment Act, 1992 (for example, rights andobligations);
- relevant sections of the Health and Safety inEmployment Regulations, 1994 (the noiseregulation).
2. Presentation of organisation’s noise managementpolicy and procedures, roles and responsibilities.
3. Presentation of plan for management of noise (forexample, 3-year plan) including where this train-ing programme for employees “fits”.
Resources
The Fact Sheets in OSH’s Management of Noise atWork: Resource Kit and Module 8: Case Studies, of thiscontrol guide.
Consider seeking the assistance of a senior manager anda employee representative official to presentorganisation and employee representative policy andattitude.
SESSION 2:
NOISE, AN
ISSUE IN THIS
ORGANISATION
MODULE 11: 14
Purpose
To practically involve employees in monitoring andsolving noise problems relevant to their work tasks.
Desirable Outcomes
I know the level of risk which I am currently facing inmy work.
I understand what could increase the level of risk (forexample, changes to current duties or workprocedures).
I know what to do if I assess that my exposure to noisesignificantly worsens.
I know some basic principles about controlling noise atsource and will make suggestions if I can see a way toreduce noise levels.
Contents
1. Measuring noise and noise exposure
- quantitative and qualitative (rule of thumb)examples(estimate dB(A)’s associated with these commontasks and look what happens as exposure timeincreases).
2. Noise levels in this organisation
- presentation of relevant workplace data (if avail-able);
- conduct walk-through survey with employees(use checklists).
3. Controlling noise exposure
- engineering control (principles and examples);
- hearing conservation (outline role of personalhearing protection briefly only, see next session).
4. (GROUP DISCUSSION) Identification of noisehazards and generation of solutions byparticipants.
- consider problems identified from walk-throughsurvey or employees’ own knowledge/experience.
If you undertake this final part of the session as aproblem-solving exercise, ensure that there is aprocedure for acting on employees’ suggestions, andreport back on what has happened as a result. Otherwisefalse expectations will be raised.
SESSION 3:
IDENTIFYING
AND SOLVING
NOISE
PROBLEMS
MODULE 11: 15
Resources
The video in OSH’s Management of Noise at Work:Resource Kit and Module 1: Case Studies and Module 2:Walk-through Audit, of this control guide.
MODULE 11: 16
Purpose
To ensure employees understand the correct selectionand use of personal hearing protection.
Desirable Outcomes
I understand that action is happening in theorganisation to reduce noise levels so that the need towear protection is minimised.
I know the type of protection most suitable for my jobnow.
I know how to obtain, use and maintain it.
I understand that if my job changes, the type ofprotection may need to change.
I will use protection appropriately.
Contents
1. Types of hearing protectors and their application
2. Choosing and obtaining hearing protectors
3. Fitting and wearing hearing protection
Resources
The video and fact sheets in OSH’s Management ofNoise at Work: Resource Kit, Module 10: Fact Sheets,and Module 12: Personal Protection, in this controlguide.
Information is available from your hearing protectorsupplier. Some suppliers may be prepared to provide aspeaker for this session.
SESSION 4:
THE EFFECTIVE
USE OF
PERSONAL
PROTECTION
MODULE 11: 17
EVALUATION Evaluation is an important tool that can provide detailsabout the effectiveness of the training and informationprogrammes that have been implemented and assistwith future planning.
The evaluation will assess:
• if objectives are being met;
• if resources are being used most effectively.
Evaluation should be a straightforward anduncomplicated exercise and need not require too manyresources.
Where findings demonstrate the effectiveness of thetraining programme, and where participants havebecome more actively involved in the noisemanagement programme, the results can be used tosupport the case for the continuation of the programmeand allocation of resources.
The following outline may assist you structure yourevaluation.
1. Describe the programme.
2. List objectives (Sample objectives for the threecategories of employees are provided in thismodule).
3. Measure appropriateness by considering:
- Whether the programme adequately addressedthe needs of the participants and what theirresponses were to it.
- Whether management responded positively to therecommendations in the report.
4. Measure effectiveness by assessing:
- The extent to which the training programme metits objectives.
- The extent to which the programme contributedto noise management.
5. Measure efficiency by considering whether theprogramme made the best possible use ofresources.
EVALUATION
OUTLINE
MODULE 11: 18
6. Report back to management and participants onevaluation findings.
7. Incorporate appropriate changes to programme.
A range of methods exist to collect the data necessary toevaluate your programme. Some methods are outlinedbelow.
Method What is recorded Example
Observation/ Behaviour Has NIHL appearedchecklist on the manage-
ment agenda?
Knowledge Knowledge and Has knowledge oftest understanding legislative
requirements ofemployers’responsibilitiesbeen raised?
Performance Specific skill/ability Are personaltest hearing
protectors beingcorrectlyfitted?
Interview/ Opinions/experiences What are partici-questionnaire/ pants’ opinionsgroup interview/ about thediscussions programme?
Record analysis Changes in the Has the pro-occurrence of gramme resulted inan event changes to occur-
rence of NIHL?
METHODS OF
COLLECTING
DATA
MODULE 12: 1
MODULE 12: PERSONAL PROTECTION
Noise managerHearing protector specialistNurse/medical staffEmployee representativesOHS committee
The purpose of this module is to assist organisationsestablish effectively managed and maintained hearingprotection programmes.
OVERVIEW
HEARING PROTECTION GRADING SYSTEM
HEARING PROTECTOR GRADING
SELECTING HEARING PROTECTORS WITHADEQUATE NOISE REDUCTION
SELECTING THE RIGHT PROTECTORS FOR EACHPERSON
COMPATIBILITY WITH THE WORK
ACCEPTABILITY TO THE WEARER
MONITORING THE USE OF HEARING PROTECTORS
HEARING PROTECTOR MAINTENANCE CHECKLISTS
PROBLEMS
FURTHER READING
THIS MODULEIS FOR
PURPOSE
CONTENTS
MODULE 12: 2
SETTING UP AN EFFECTIVEPERSONAL PROTECTION PROGRAMME
The key requirements for an effective personal hearingprotection programme are that:
• management clearly supports the programme in awritten policy and by example;
• managers, supervisors and employees are aware oftheir responsibilities;
• each wearer is fitted with adequate, comfortableand acceptable hearing protectors;
• wearers are given information and training toprovide necessary knowledge and skills;
• noisy areas are signposted;
• noisy, portable equipment is labelled;
• regular checks are made of wearing rates andpractices;
• feedback is provided to wearers and managers of theresults of checks;
• protectors are regularly cleaned;
• there are frequent maintenance checks of protec-tors and prompt replacement of worn or damageditems;
• wearer problems are dealt with promptly andsympathetically;
• wearers are aware that the programme is part of amore comprehensive noise management pro-gramme that aims, wherever possible, to reducenoise levels progressively to the point where hear-ing protectors will not be required.
Many of the above points are mentioned in Step 4 of theCORE. This module goes into a number of issues ingreater detail and provides a list of useful publications.
Hearing protectors are currently tested and graded inNew Zealand by the Institute of Environmental Science& Research with the assistance of the NationalAudiology Centre, in Auckland.
OVERVIEW
HEARINGPROTECTION
GRADING SYSTEM
MODULE 12: 3
The protectors are tested to the International Standard,ISO 4869 or Australian Standard AS1270. This uses asubjective method to determine how well they performat reducing different frequencies of sound. It is anattempt, in the laboratory, to assess how they willperform when used properly in a work situation. Theireffectiveness at reducing (attenuating) noise determinesinto which Grade they are placed.
For example, in order to be a Grade 1 protector, it mustbe able to reduce a noise level of 91 dB(A) outside, to nomore than 85 dB(A) inside the device. This is areduction of at least 6 dB(A). It will not get into Grade2 if it cannot reduce the level by at least 12 dB(A), andso on.
Hearing protectors are assigned to one of five hearingprotection grades according to their acousticperformance. They should be selected on the basis ofthe Noise Exposure Level (L
Aeq,8h) or the Peak Level
(Lpeak
) to which an employee is exposed.
HEARINGPROTECTOR
GRADING
Hearing LAeq,8h Lpeak Types of SuitableProtection (dB(A)) (dB) Hearing ProtectionGrade Device
1 86 - 91 141 - 46(1 ) Earplugs or earmuffs2 92 - 97 147 - 152(1 ) Earplugs or earmuffs3 98 - 103 153 - 158(1 ) Earmuffs4 104 - 109 159 - 164(1 ) Earmuffs5 110 - 115 165 -170(1 ) Earmuffs5 >140(2 ) Earmuffs+earplugs
(1 ) Where LCFMax
- LAFMax
< 5 (LCFMax
is the Maximum, C-weighted, “Fast” time-responselevel)
(2 ) Where LCFMax
- LAFMax
≥ 5 (LAFMax
is the Maximum, A-weighted, “Fast” time-responselevel)
There are two methods used for calculating the noisereduction required of hearing protectors for givenexposure conditions:
• The GRADING SYSTEM (which uses a method similarto the Australian SLC80 method) requires only asingle measurement, that is, of the A-weighted
TABLE 1: NOISE
EXPOSURE
GRADES
SELECTINGHEARING
PROTECTORS WITHADEQUATE NOISE
REDUCTION
MODULE 12: 4
sound pressure level (LAeq,T
) of the noise to deter-mine the Noise Exposure Level, L
Aeq,8h, together with
the ‘Peak’ sound pressure level in the case ofimpactive or impulsive noise. This is the methodnormally used for hearing protector selection inindustry.
• The OCTAVE BAND METHOD is more accurate butrequires that the frequency content of the noise bemeasured in at least seven octave bands. In prac-tice, its use is restricted to situations involving avery high level noise or noise with intense tonal,infrasonic or ultrasonic components. These situa-tions are rare in industry.
An alternate single number rating — the NRR — isused to rate hearing protectors in the USA. TheNRR value is usually much higher than the Austral-ian SLC80 value and the reduction indicated by thegrading of the device in New Zealand. NRR has notbeen standardised in either New Zealand or Aus-tralia and should not be used.
The appropriate type of hearing protector for agiven exposure condition therefore normallyrequires only the determination of the Noise Expo-sure Level (L
Aeq,8h) and the Peak Level (L
peak).
Suppose hearing protectors are to be selected for anemployee whose typical daily noise exposure pat-tern is as shown in the following table:
Machine/Process Measured Exposure Partialnoise level Duration Noise
LAeq,T Exposure(dB(A)) (Hours) (Pa2h)
Furnace 105 0.5 6.5
Chipping hammer 96 4.0 6.4
Power hacksaw 88 1.5 0.4
Welding 90 2.0 0.8
Daily Noise Exposure (DNE) 14.1
The correct way to select an appropriate hearingprotector is to determine the LAeq,8h for this exposureand select the appropriate grade from Table 1 above.
TABLE 2: TYPICAL
DAILY NOISE
EXPOSURE DETAILS
FOR AN
EMPLOYEE
WARNING:
MODULE 12: 5
In this example, a DNE of 14.1 Pa2h is an LAeq,8h
of 96dB(A). (See Core Module Appendix 2 for the method ofdetermination).
The appropriate protector to be selected is thereforeGrade 2.
An operator works in an area for eight hours where thenoise level is 88 dB(A). There are also transient noisespresent which produce Peak levels of 155 dB. Thetransient noise gives a maximum C-weighted fastresponse level of 112 dB(C), and a maximum A-weighted fast response level of 110 dB(A). What is thehearing protection grade for the area and what type ofhearing protection should be worn?
The employee is exposed to an LAeq,8h
of 88 dB(A), and aL
peak of 155 dB with an L
CFMax - L
AFMax < 5.
The type of protection required to protect against theLAeq,8h of 88 dB(A) is Grade 1.
The Lpeak of 155 dB requires Grade 3 protection.
The Hearing Protection Grade required is therefore thehighest of these requirements, Grade 3. The type ofhearing protection to be selected is therefore Grade 3earmuffs.
A common approach to selection of a protector is to usethe highest dB(A) level to which the employee isexposed. This is a “super safe” approach since it meansthe employee will be adequately protected even ifexposed all day to the highest dB(A) level measured intheir working environment.
In the present example in Table 2, the highest noiselevel is 105 dB(A). The hearing protector selected usingthis “super-safe” approach would need to be Grade 4(which gives protection up to 109 dB(A)).
Two qualifications to this basic procedure are worthremembering.
It should be noted that the grading system does notguarantee adequate protection for all wearers, even
A SIMPLE
EXAMPLE:
ANOTHER
APPROACH
AVOIDING UNDER-
PROTECTION
MODULE 12: 6
when the correct grade device is used. The system willonly give adequate protection in approximately 84% ofcases. Also, when an unusual noise is present,particularly one containing high levels of low-frequencysound, adequate protection may also not be achieved.
It is therefore common practice to select a protectorwith a grading of 1 greater than the calculatedrequirement.
In the present example, in which the requirement isGrade 2, common practice would be to select hearingprotectors with a grading of 3.
While it is obvious that under-protection should beavoided, over protection is also undesirable. This isbecause it may lead to the selection of unnecessarilyheavy or tight protectors, create communicationproblems and make the wearers feel isolated from theirsurroundings. Protectors may be tampered with orused only part-time as a result, and the effectiveprotection will then be much less than would have beenobtained with more carefully chosen devices (see figure1 (page10)).
This point can be illustrated by further analysis of theexample considered above. Suppose Grade 5 hearingprotectors were chosen for the person whose typicaldaily noise exposure was shown in Table 1. The dB(A)levels to which the employee would be exposed whenwearing the protectors may be estimated by subtracting30 dB(A) from each of the dB(A) levels. This leads tothe situation shown in Table 3.
Machine/Process Noise level Effective Exposure Partial NoiseLAeq,T Noise Level Duration Exposure(dB(A)) LAeq,T (Hours) (Pa2h)
(dB(A))
Furnace 105 75 0.5 0.0065
Chipping hammer 96 66 4.0 0.0064
Power hacksaw 88 58 1.5 0.0004
Welding 90 60 2.0 0.0008
Daily Noise Exposure (Pa2h) 0.0141
AVOIDING OVER-
PROTECTION
TABLE 3:
ESTIMATED DAILY
NOISE EXPOSURE
DETAILS FOR THE
EMPLOYEE IN
TABLE 2, WHEN
WEARING GRADE
5 HEARING
PROTECTORS
MODULE 12: 7
The protectors have reduced the employee’s daily noiseexposure from 14.1 to 0.0141 Pa2h, a very considerablereduction and much more than is really necessary.0.0141 Pa2h is equivalent to an L
Aeq,8h of 66 dB(A).
Hearing protectors with lower noise reduction couldsafely be considered. Suppose, for example, that Grade2 protectors were selected (as they should have been).Then the employee’s estimated exposure would be asshown in Table 4. It may be assumed that Grade 2protectors reduce the noise level by 12 dB(A).
Machine/Process Noise Effective Exposure PartialLevel Noise Level Duration Noise
LAeq,T LAeq,T Exposure(dB(A)) (dB(A)) (Hours) (Pa2h)
Furnace 105 93 0.5 0.40
Chipping hammer 96 84 4.0 0.40
Power hacksaw 88 76 1.5 0.02
Welding 90 78 2.0 0.05
Daily Noise Exposure (Pa2h) 0.87
The employee’s estimated daily noise exposure is stillonly 0.87 Pa2h, which is equivalent to a noise exposurelevel, LAeq,8h of 84 dB(A). Clearly, Grade 2 protectorswould be quite adequate in this situation.
This example shows that selecting hearing protectorssolely on the basis of noise levels, that is, without takingaccount of exposure duration, can lead to unnecessaryover-protection with potential problems for the wearer.
If such problems are likely to arise, the solution is toundertake a more detailed analysis of the exposureconditions, taking account of exposure duration as wellas noise levels, and select a protector with less — butstill adequate — noise reduction, as in Table 4 above.
Once the range of available protectors is narrowed tothose with adequate noise reduction, the next objectiveis to ensure that each wearer is correctly fitted with asuitable and acceptable device. No single hearingprotector suits everybody so it is important for wearersto be individually fitted.
TABLE 4:
ESTIMATED DAILY
NOISE EXPOSURE
DETAILS FOR THE
EMPLOYEE IN
TABLE 2, WHEN
WEARING GRADE
2 HEARING
PROTECTORS
SELECT THERIGHT
PROTECTORSFOR EACH
PERSON
MODULE 12: 8
To ensure that earmuffs fit, a wearer should be able toanswer “yes” to the following questions:
• Can the ears be fitted comfortably inside the ear-muff shells?(The cushions should not press the ears against thehead but should surround them. Some earmuffsare deliberately designed so that the openings intothe shells are fairly narrow while the shells them-selves are quite spacious. This is done to improvenoise reduction. It may be necessary to manipulatethe ears through the openings when putting theearmuffs on. Provided the ears can resume theirnormal shape once inside the shells, this is not aproblem.)
• Can the headband be adjusted so that the earmuffsare held firmly in place?
• Can the headband be adjusted so that the cushionpressure feels evenly distributed around the ears?
• Is the weight of the muffs comfortably supported?
• Is there a close fit between the cushions and thehead so that there are no gaps?(Some common causes of gaps are prominentcheekbones, a deep groove behind the jaw belowthe ear, thick hair and beards).
• Is there a noticeable reduction in the loudness ofsounds?(The best place to fit hearing protectors is in noisysurroundings, ideally the workplace in which theywill be worn. If a reduction in loudness is notclearly noticeable, the fit is inadequate).
It takes time and practice to fit earplugs correctly.People who have never worn earplugs before should, ifpossible, be shown what to do by an experienced fitteror user. Techniques for earplug fitting are illustrated inModule 10: Fact Sheets.
To ensure that earplugs fit, a wearer should be able toanswer “yes” to the following questions:
• Can the earplugs be fitted without difficulty?(Persons with impaired finger dexterity, as a result
EARMUFFS
EARPLUGS
MODULE 12: 9
of arthritis or injury for example, may be unable touse earplugs).
• Are the earplugs comfortable?(It takes 2-3 weeks for people who have not wornearplugs before to get used to them. Early judge-ments of comfort may not be reliable).
• Do the earplugs appear to be firmly seated in theear canals?
• Do you experience a noticeable reduction in theloudness of sounds?(If not, the fit is inadequate).
It is essential that the selected hearing protectors do notinterfere with the wearers’ work and, conversely, thatthe requirements of the job do not interfere with theproper functioning of the protectors. Problems ofequipment compatibility have recently been addressedby several safety equipment manufacturers. Shoparound if compatibility problems arise.
To ensure that the wearing of earmuffs is compatiblewith the work, wearers should check if:
• they are able to move freely without dislodging theprotectors;
• they are still able to gain access to confined spaces(for example, for machine maintenance) withouthaving to remove the protectors;
• there is any interference between the protectorsand other equipment worn, such as a weldingshield, a cap, a respirator, eyeglasses or goggles.
To ensure that the wearing of earplugs is compatiblewith the work, wearers should check if:
• There is a need to remove and replace protectorsfrequently. If there is, earmuffs or ear caps may bemore convenient.
• Their hands are likely to be soiled by work. If theyare, earmuffs may be more convenient.
COMPATIBILITYWITH THE
WORK
EARMUFFS
EARPLUGS
MODULE 12: 10
To be effective, protectors must be worn all the timewhenever the wearer is in the presence of hazardousnoise. To be worn all the time, the protector must behighly acceptable to the wearer. Giving employees freechoice from a range of protectors, subject of course tosatisfactory fit and comfort, has been found tosignificantly improve acceptability. Once three or fouradequate protectors have been identified, therefore,employees should be given free choice between them.
Employees are also likely to find hearing protectorsmore acceptable if they are aware that the organisationis working towards progressive noise reduction.Publicising the organisation’s noise policy and noisecontrol plan will also help boost hearing protectoracceptability.
The removal of hearing protectors for even shortperiods of time can dramatically reduce theireffectiveness and lead to under-protection for thewearer (see figure 1 below).
ACCEPTABILITYTO THE
WEARER
FIGURE 1:
REDUCTION IN
THE EFFECTIVE
PROTECTION
PROVIDED BY A
GRADE 5 HEARING
PROTECTOR WITH
DECREASED
WEARING TIME IN
A GIVEN NOISE
ENVIRONMENT
Due to the difficulties of wearing hearing protectors forlong periods of time in some environments, it isimportant that regular brief rest periods in quiet areas beprovided, to maximise the proper use of protection whenneeded.
MODULE 12: 11
Over a working day, periods of a few minutesunprotected exposure are easy to accumulate, forexample by placement and removal of the protectorswhile in the noisy area rather than before entering andafter leaving it; or by removing hearing protectorsbriefly for purposes of comfort, communication or anyother reason.
(a) If not worn for 15 minutes during a total expo-sure time of 1 hour (worn 75% of the time), theeffective protection provided by a Grade 5 (30 dB)hearing protector is only 6 dB. This means thatworn in this way, the Grade 5 protector effectivelygives the same protection as a Grade 1 protectorworn all the time (for the full hour of exposure).
(b) If not worn for 5 minutes during a total exposuretime of 6 hours (worn 98.6% of the time), theeffective protection provided by a Grade 5 hearingprotector is only 18 dB; the effective protectivevalue is 2 Grades (12 dB) lower than expected.
It cannot be overemphasised that, in order to giveadequate protection, a hearing protector must be wornfor the entire time of exposure to excessive noise. Ifthere is any exposure to excessive noise through lack ofwearing, the use of a higher grade protector thannecessary when it is worn will not compensate for thisexposure.
Once accumulated, noise exposure cannot be takenaway.
Frequent checks should be carried out to ensure thathearing protectors are worn correctly and consistently.This is especially important in the early stages of apersonal hearing protection programme and for newemployees who may not have used hearing protectorsbefore, or who have not previously been shown how touse them correctly.
Correct wearing means always fitting and wearing theprotector according to instructions supplied with thedevice. If no instructions are available, use the generalfitting instructions in Module 10: Fact Sheets, which
MONITORINGTHE USE OF
THE HEARINGPROTECTORS
EXAMPLES
MODULE 12: 12
also illustrates some common fitting errors to avoid.
Consistent wearing means always wearing protectorswhenever the surrounding noise level is such thatvoices have to be raised to communicate over a distanceof a metre, that is, when the noise level is over 85 dB(A).
The safest and most practical rule for hearing protectorusers is always to wear protectors whenever the noiselevel reaches 85 dB(A), regardless of exposure duration,and many organisations now incorporate this rule intheir hearing protection programmes.
Supervisors are usually best placed to undertake thesechecks since they are in constant contact with wearers.Other managerial staff, especially the noise manager,should also be involved. Anyone undertaking thesechecks should be familiar with the contents of thismodule and the Fact Sheets on hearing protectors.Ideally they should also have received some basictraining from the hearing protector supplier(s).
To sustain interest in the personal protectionprogramme and to encourage consistent and correctusage of earmuffs and earplugs, provide feedback toemployees on the results of monitoring usage. Forexample, graphs or “thermometer-type” scales could beused to post weekly “per cent wearing rates” and “percent correctly worn rates” results on a prominent noticeboard. These data should also be given to management.They are especially useful for highlighting problems,but are also useful for demonstrating progress. Severalresearch studies have confirmed the value of this type offeedback in helping develop optimum usage rates.
All hearing protectors except disposable earplugs shouldbe checked at least once a month, using the followingchecklists. All types of protectors should be inspectedfor cleanliness and, where necessary, cleaned.
If the answer to any of the following questions is “yes”,then the relevant part should be replaced:
WHO SHOULD
CHECK?
FEEDBACK
HEARINGPROTECTOR
MAINTENANCECHECKLISTS
EARMUFFS
MODULE 12: 13
• Has the headband lost tension?(Lay the muffs on a bench and check that the gapbetween the cushions is no greater than on a newpair of the same kind).
• Is there any possibility of an air leak where theheadband is attached to the shells?
• Are there any holes or cracks in the plastic shells?
• Are there any creases or grooves in the cushions?
• Are the cushions torn or split?
• Are the cushions harder than new ones?
• Are the foam liners inside the shells damaged orhardened?
Compressible Foam Types
Compressible foam plugs are maintenance-free as theyare basically disposable, though they can be re-usedseveral times if kept clean. They should be washed inwarm soapy water as necessary and allowed to drybefore being worn again.
Rubber or Plastic Types
If the answer to any of the following questions is “yes”,then the rubber or plastic earplugs should be replaced:
• Are any parts missing?
• Does the plug have any splits or holes?
• Is the plug harder than a new one?
• Is the plug a different shape from a new one?
A system should be established for dealing withproblems which wearers experience with hearingprotectors. A basic system would be for wearers first toapproach their supervisor, then to be referred to thenoise manager and/or hearing protector specialist if thesupervisor is unable to resolve the problem.
Those responsible for supervising the use of hearingprotectors and dealing with problems need relevantbasic training. Other sources of help include
EARPLUGS
PROBLEMS
PROBLEM-
SOLVING
RESOURCES
MODULE 12: 14
Management of Noise at Work: Resource Kit, othersupervisors, the organisation’s noise manager, hearingprotector specialist, nurse, safety officer, the hearingprotector supplier and the occupational health andsafety services of relevant employer associations,employee representatives and Occupational Safety andHealth. Some helpful publications are listed at the endof this module.
It can take 2-3 weeks for people to become accustomedto wearing hearing protectors. If discomfort persistsafter that time the problem needs to be investigatedcarefully and sympathetically.
If the wearer has chosen his or her own hearingprotector from a suitable range in accordance with theselection guidelines above, the incidence of discomfortproblems will be minimised. However, some discomfortproblems become apparent only after a period of actualuse (for example, there might he a slowly developingsore spot where earmuffs are pressing eyeglass armsagainst the head). Possible solutions are to fit specialfoam pads over the arms (contact the earmuff supplier,hearing in mind that these pads can reduce noisereduction by up to 1 Grade (3-6 dB)), try differentearmuffs, fit narrow eyeglass arms or change toearplugs. If the problem persists it may be necessary torefer the wearer to an experienced audiologist, hearingconservation consultant or doctor.
A person may not be convinced of, or seriouslyconcerned about, the risk of hearing damage. If so,check that they have been given the relevant fact sheetsfrom Module 10: Fact Sheets and talk over the mainpoints, refer to the workplace noise survey to point outplaces and equipment where hazardous noise levelshave been measured, explain the organisation’s plans forfuture noise reduction, and point out that employeesare under a legal obligation to use hearing protectors indesignated areas.
In situations where employees are reluctant to wearhearing protectors even if they are aware of the risk,
DISCOMFORT
NON-WEARING
RELUCTANCE TO
WEAR
MODULE 12: 15
there may be an underlying problem. For example,some employees may already have some degree ofhearing impairment and be concerned that they will nothear warning sounds. Such problems need carefulinvestigation and may require referral to an audiologistor other specialist.
Difficulties experienced by employees are notuncommon, especially if hearing protectors have to beworn for long periods. The use of hearing protectorsintroduces uncertainties into this mode of risk controland highlights the importance of long-term planning toremove noise hazards wherever possible.
Australian Standard AS 1269, Acoustics - HearingConservation.
Gasaway, D.C., Hearing Conservation - A PracticalManual and Guide, Prentice-Hall Inc., New Jersey,1985.
Gasaway, D.C., “Motivating Employees to Comply withHearing Conservation Policy”, Occupational Health andSafety, June, p. 62-7, 1984.
National Acoustic Laboratories, Attenuation of HearingProtectors, 7th Edition, AGPS, Sept 1994. (Availablefrom Australian Government Publishing ServiceBookshops which are in all capital cities and from theNational Acoustic Laboratories, Chatswood, NSW,phone (+61 2) 412 6920 or (+61 2) 412 6890.)
Occupational Safety and Health Service, List of GradedHearing Protectors, available from your local branch ofthe Occupational Safety and Health Service,Department of Labour (included in Management ofNoise at Work: Resource Kit).
Royster, J.D. and Royster L.H., Hearing ConservationProgrammes, Practical Guidelines for Success, LewisPublishers, 121 South Main St, Chelsea, Michigan,1990.
Several manufacturers and suppliers of hearingprotectors also produce excellent information andtraining materials.
LONG-TERM
WEARING OF
PROTECTORS
FURTHERREADING