Noise at Work Regulations

Mick Gray MRSC, LFOH, ROH.

MWG Associates Ltd

The Issue

• NIHL is a significant occupational disease

• 170,000 people in the UK suffer deafness, tinnitus or other ear conditions as a result of exposure to excessive noise at work – Health and Safety Executive

• 3rd European workers are exposed to potentially dangerous levels of noise for at least a quarter of their working time – European Agency for Safety and Health at Work

• “ the most prevalent, irreversible industrial disease” - World Health Organisation

Programme

• Basic Noise Terminology

• The Control of Noise at Work Regulations

2005

• Instrumentation for Workplace Noise

Basic Noise Terminology

An introduction to noise and sound

• What is noise?

– Noise is usually defined as “unwanted sound”

• But unwanted by whom?

• Let us consider the more general case of

“sound”

Basics of Noise Terminology

• One of the 5 human senses -

– sight, touch, taste, smell, hearing

• Pressure variations in the air caused by something

moving

• detected by our ears and turned into electrical

impulses

• ear is divided into 3 parts,

– outer, middle and inner ear

• brain sorts them out into some form of meaning

The physics of hearing

• we hear sounds over a wide range of frequencies

– measure frequency in Hz

– Hz is short for Hertz or cycles per second (cps)

• we hear sound over a wide range of levels

– measure levels in dB

– dB is short for decibels

• we hear sound over a wide range of times

– measure time in seconds, minutes or hours

dB Scale

What do we hear?

• Air pressure fluctuations are caused by vibrating objects or by air flows

• low speed variations cause low frequency sounds

– few tens of variations per second

• high speed variations cause high frequency sounds

– few thousands of variations per second

• variations are called frequency or tone or pitch

• limits of normal healthy hearing is about 20 to 20,000 Hz in the very best case

The inequality of human hearing - 1

• We do not hear all sounds with equal intensity

• our ears are less sensitive to some frequencies than

others

• this is more noticeable at the lower frequencies of

sound

• consider some sounds as examples……

• Hum of power transformers, air conditioning, etc

The inequality of human hearing - 2

• our hearing is non-linear unlike the response of a

hi-fi amplifier

• it is also non-linear with the loudness (or strength)

of the sound

• research has established 3 main areas of interest

associated with noise measurements

• standardized correction curves have been written

into the way measurements are carried out

The equal loudness curves

• Lowest

curve

shows the

threshold of

hearing

(audibility)

for normal

adult male

• Phon

curves

Frequency weighting curves -1

• For low level measurements correction curve is quite steep

– the A weighting curve

• for medium level measurements the correction is less steep

– the B weighting curve

• for high level measurements the correction is only at the extremes

– the C weighting curve

The frequency correction curves

• The „A‟

curve is at

40 Phons,

the „B‟

curve is at

70 Phons,

the „C‟

curve is at

100 Phons

The standard broadband frequency

weightings for noise measurements

Frequency weighting curves - 2

• for some measurements the “true” or un-corrected frequency response is needed

– (sometimes called Linear or un-weighted or All-Pass)

– this can be different for different manufacturers and for different instruments from the same manufacturer depending on microphone fitted

• the Z weighting curve sets limits of 20 to 20kHz

What do we hear?

• How loud is it?

• Very wide range of sound pressures experienced

• Sound pressure is measured in Pascals (N/m2)

• lowest values few tens of micro Pascals (10-5 Pa)

• highest values are about 100/200 Pa

• this is a range of at least 106

• this is a ratio of over 1 million to 1!!

What range do we hear?

• If we measured this like we do with

temperature or length,…..

– We would need a tape measure that could

measure 1 mm and 1 km!! (1 thou to 83 ft)

• This would be very difficult to express results

if we had to use absolute units of sound

pressure, so….

How do we measure sound?

• We use a relative scale rather than an absolutescale

• we say a sound is bigger (or smaller) than another sound by a certain amount

• logically we would choose a pressure of 1 Pa

– (like 1 Volt for electrical signals)

• but then we would end up with a scale of smaller and bigger values, so….

How do we measure sound?

• We choose the lowest pressure that the normal ear can hear as our reference point

• in this way all other sounds are always bigger than that sound

• First we need to have a reference pressure level

– 20 micro Pascal at 1 kHz has been internationally agreed

The dreaded decibels!!

• Actual equation used to find the dB value of a given sound pressure is found from -

• dB = 20 log (P/Pref) Pref = 0.00002 Pa

• because of the logarithmic nature of the dB scale

• 70 dB + 70 dB (does not =) 140 dB

• 70 dB + 70 dB = 73 dB

The maths of dB‟s

• The reference sound pressure corresponds to the lowest sound that can be normally heard

• now we refer all other sounds to this level

• a sound 10 times more would be +20 decibels (dB)

• a sound 100 times more would be +40 dB

• a sound 1000 times more would be +60 dB

• a sound pressure twice as much would be 6 dB

• (Note that a sound with twice the noise energy increases by 3dB)

The R.M.S. time constants

• We use the result of the R.M.S. circuit to see the

noise level on the display

• for steady noises we use the time averaged levels

– slow (1 sec), fast (1/8 sec), impulse (1/32 sec)

• these settings are standardized on meters to allow

comparisons to be made

• There is a Peak setting on some meters to capture

the true highest level (equivalent to <1/10,000sec)

What do we measure?

• Definitions of some of the popular noise units as we

come across them in the sessions later on

• Instantaneous sound pressure level L

• maximum sound pressure level Lmx

• minimum sound pressure level Lmn

• peak sound pressure Lpk

• time average sound pressure level Leq

Example of the steady level

LAEQ = 83 dB

70

80

90

TIME

LA

How do we state the result?

• Need to specify the frequency weighting

– A, C or Z (non)

• need to specify the time weighting

– S, F or I

Expression of typical noise result

• For example, the noise level from a source -

– maximum A weighted Fast sound pressure level

was

85 dB over a 3 min period

– written as LAFmx = 85 dB (3 min)

Lepd for a 4 Hour Shift

1 2 3 4 5 6 7 8 9 10 11 12

LAeq

85

86

87

88

89

90

LAeq

Lepd

• Steady LAeq

90dB

• Noise is

measured for 4

hours

• Energy is

“spread” over

8hrs

• Therefore Lepd is

87dBA

Lepd for an 8 hour Shift

1 2 3 4 5 6 7 8

LAeq

80

82

84

86

88

90

LAeq

Lepd

• 8 hour LAeq

= Lepd

• Steady noise

of 90dBA for

8 hours =

90dBA Lepd

Lepd for 12 hour shift

• Employee is exposed to 4 hours “extra” energy, therefore Lepd is higher than measured LAeq

• 12 hours of steady 90dBA = Lepd of 92dBA

1 2 3 4 5 6 7 8 9 10 11 12

LAeq

85

86

87

88

89

90

91

92

93

94

LAeq

Lepd

The peak level limit

• Although LEP,d is an 8 hours value.

• But very high impulses of noise can cause

instant damage to hearing.

• So instruments have peak hold function to

measure any impulsive noises (LCPK).

• Only has to be exceeded once to be

considered over action level.

Introduction to noise

• Conclusions

– noise (sound) has three dimensions

• frequency

• level

• time

• Must measure properly to ensure you get the

correct values

Physical Agents (Noise) Directive

Directive 2003/10/EC

The Control of Noise at Work Regulations

2005

Below first action level

Employer must:

• Reduce risks to lowest practicable level

• Keep records and make them available including

audiometry (if done)

• Buy quiet

Above first action level

Employer must:

• Identify all employees at risk

• Put up signs

• Review if any changes to noise levels

• Repeat assessment <2 years

• Inform employees of risk

• Provide choice of PPE on request (first aid)

• Provide training / education

• Noise Control

Above second action level

Employer must:

• Demarcate as Ear Protection Zones

• PPE must be used at all times

• Noise control to reduce exposure

• If Lepd is over 95dBA then must use octave band method to check if hearing protection is effective

Note: For peak action level, take the same action as for second action level

Why the changes?

• Even under current regulations many people

are still exposed to unacceptable levels of

noise.

• 14% of population exposed to noise in the

workplace will suffer some long term damage

New regulations give new emphasis

What is new emphasis?

• Main goal is control of noise risk

• Risk assessment to establish what needs to be done

• Controls known to work should be implemented

• PPE in place

• Other systems in place

– Maintenance

– Training

– Health surveillance

Action level changes

First action level:

Becomes Lower Exposure Action Value

• 80dB(A) LEP,d (Reduction of 5dB)

• New: 112 Pascals (LCPK= 135dB)

• Take the same actions as first action level in

current regulations

Action level changes

Second action level:

Becomes Upper Exposure Action Value

• 85dB LEP,d (Reduction of 5dB)

• 140 Pascals (LCPK= 137dB)

• Take the same action as second action level in

current regulations

Exposure limit value

• 87dB(A) LEP,d exposure limit

• 140dB LCPK exposure limit (200 Pascals)

• Is the maximum permissible estimated operator noise dose whilst wearing (and not wearing) hearing protection

• Value at the ear after taking into account any PPE

• Therefore necessary to calculate effectiveness of PPE

• NOT a target, but minimum acceptable

• Target these individuals first

140 dB

90 dBA

85 dBA

Currently –

(86/188/EEC)

From April 06 -

(2003/10/EC)

Peak Action

Level

Second Action

Level

First Action

Level

d

B

140 dB Peak Limit Value at ear

87 dBA Exposure Limit Valueat ear

137 dB Peak level at Upper

Exposure Action Value

85 dBA Upper Exposure Action

Value

80 dBA Lower Exposure

Action Value

135 dBPeak level at Lower Exposure

Action Value

Weekly noise exposure level

• Calculate if there is significant variation of

dose on a daily basis

• Take log average of estimated daily doses

• Apply action levels as normal

Audiometry

• Employees over the second action level have

the right to a hearing check (audiometric test)

• As a preventative measure individuals who

may be susceptible to noise below this level

should also be tested e.g. those with previous

damage.

Risk Assessment

• Assess risks to Health and Safety

• Done to identify actions to reduce risks

• Necessary when lower action levels likely to

be exceeded

• Should assess exposure, measure if likely to

be above second action levels

New exposure tool

• Exposure points have replaced nomogram

– Converts Laeq or LCPK into exposure points

– Converts EP into LEP,d

• Meant to allow easier assessment of higher

risk activities

The „competent person‟?

• Competent person will not appear in regs

• Risk assessment/control measures to be

competently planned and carried out

• Rely on „expert intermediaries‟ for advice and

services where necessary

• Guidance will be given to judge when advice

is needed

Need to measure for correct hearing

protection where necessary

• Octave Band Method

Needs frequency analyser 31.5Hz - 8KHz

• High, Medium and Low (HML) Method

Needs C and A weighted LEQ

• Simplified Noise Reduction (SNR) Method

Needs C weighted LEQ

Octave band is the preferred method

Summary

• Asses the risks

– Decide on control measures

– Qualitatively or quantitatively, with due regard to

precision

• Reduce risks for all employees

• Hearing protection for residual risks

• Health surveillance

Implications

• Cost

• New assessment

• Review PPE

• Increase noise control

• Action plan

• Time

When will it be implemented?

• The Control of Noise at Work

Regulations 2005, ISBN 0110729846

• 6th April 2006

• http://www.hse.gov.uk

Instrumentation for Workplace

Noise Assessments

S.L.M. or Dosimeter?

• Two main types of instrument are used to

perform workplace noise assessments

– Sound Level Meter (SLM)

– Dosimeter

When to use an SLM

• Is the preferred method of measuring Noise

at Work

– At the ear (10-15cm) pointing at noise source

– Measure both ears

• Can only do this easily for „stationary‟ jobs

– Need to measure for each „job‟ and calculate

Lepd

When to use a Dosimeter

• Dosimeters are easier but have to be aware of possible errors

– Tampering

– Body reflections

• Use Dosimeters for:

– Mobile workers

– Complex work patterns

– Walk through management

• Research shows will get a higher reading with dosimeter compared to SLM

Instrument Accuracy

• Different accuracies are available:

– Type 0 (laboratory standard)

– Type 1 (precision grade for consultants/environmental)

– Type 2 (general purpose grade)

• These „Types‟ are also knows as „Class‟

– Type 2 is minimum required for Noise at Work

Other considerations

• Instruments must be field checked before use

– Use an acoustic calibrator, ideally in area where they are to be used

• Must have a valid calibration certificate

– UKAS or Manufacturers standard

– Every 2 years for instrument and calibrator

• Good practice to always use a windshield

– Protects from dust and knocks

Other considerations

• Acoustic Standards

– Sound Level Meters to IEC60651 and IEC60804

– Newer standard is IEC61672 for SLMs

– Calibrators to IEC60942 (2003)

– Dosimeters to IEC61252

General Instrument Categories

• SLMs

– Simple SLMs (No Leq)

– Integrating SLMs (Leq)

– Octave Band SLMs for hearing protection

– Other applications (e.g. environmental)

• Dosimeters

– Logging or non logging

Simple SLMs

• Simple point and shoot

• Displays db level

• Low cost

• Only suitable for steady noise

levels

• Class 2

Integrating SLMs

• Give Leq Level

• Measure simultaneous Leq and

Lcpk

• Low cost

• Variable or impulsive noises

• Class 2 or Class 1

• Lceq and Laeq for HML method

Frequency Analysis

• Used for selection of hearing protection

• Sequential or real time

– Caution with sequential!

• Also integrating (Leq)

• Class 1 or 2 only

• Other applications (e.g. environmental)

Other applications

• Environmental

– Protect microphone?

– Need real time analysis

for frequency

• Different parameters and times

– Leq, L90, Lmax etc,

– 5min, 1hr intervals?

Dosimetry

• 2 main solutions

– Dosemeter

– Dosebadge

• Both solutions have advantages

over each other

Dose Badge & Reader

• Small size

• Inexpensive for quantity

• Noise at work only

• No cable

Dosimeter

• Dual purpose (SLM or Dosi)

• International standards built in

• Download and control software

• Automatic report generation

• Comprehensive measurements

• I.S. Models available

Calibrators

• All instruments should be

calibrated prior to

measurement

•Class 1 or 2

•Automatically adjusts for

cavity

Conclusions

• Different instruments for different:

– Noise types

– Workers/Jobs

– Work patterns

• Field calibrate your unit, and have it

regularly calibrated in a laboratory