10/1/99 Created By: C. Miterko 1

29 CFR 1910.95

القوى على الحفاظ برنامجالسمعية

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What is Sound? What is Sound? الصوت هو الصوت ما هو ما•Sound is what we hear and Sound is what we hear and is produced by vibrating is produced by vibrating objects and reaches the objects and reaches the listener’s ears as waves in the listener’s ears as waves in the air or other media.air or other media.•When an object vibrates it When an object vibrates it causes slight changes in air causes slight changes in air pressure. These air pressure pressure. These air pressure changes travel as waves changes travel as waves through the air and produce through the air and produce sound. sound.

إهتزاز من ينتج إهتزاز الصوت من ينتج الصوتعلى ويكون على األشياء ويكون األشياء

إلى تصل موجات إلى هيئة تصل موجات هيئةاألذن.األذن.

األشياء تهتز األشياء عندما تهتز عندماتغيير لذلك نتيجة تغيير يحدث لذلك نتيجة يحدث. الهواء ضغط فى .بسيط الهواء ضغط فى بسيطضغط فى التغيير ضغط وهذا فى التغيير وهذا

الهواء فى ينتقل الهواء الهواء فى ينتقل الهواءموجات شكل موجات على شكل علىتنتج بدورها تنتج والتى بدورها والتى

الصوتالصوت

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يهتز ، العصاة بواسطة الطبلة خبط يتم عندمالألمام الطبلة سطح يتحرك وعندما الطبلة سطح

يتحرك وعندما الهواء ضغط فى موجب تغيير يحدثضغط فى سلبى تغيير يحث للوراء الطبلة سطح

موجات شكل على الضغط هذا يتحرك وهكذا الهواء. الصوت ونسمع لألذن يصل حتى

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What is Noise?What is Noise?

األصوات هى األصوات الضوضاء هى الضوضاءبها المرغوب بها غير المرغوب غير

Hertz (Hz)Hertz (Hz)

الهيرتز بوحدة يقاسالتى الذبذبات عدد وهى

ضغط تغيير من تنتجالثانية فى الهواء

الواحدة

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FrequencyFrequency

Humans can typically hear Humans can typically hear between 20 - 20,000 Hzbetween 20 - 20,000 Hz

األصوات البشرية األذن األصوات تسمع البشرية األذن تسمعهيرتز هيرتز 2000020000 – – 2020بين بين

العادى بالحديث الخاص العادى التردد بالحديث الخاص الترددحدود فى حدود يكون فى هيرتز هيرتز 30003000يكون

الجيدة الصحة ذو الجيدة اإلنسان الصحة ذو اإلنساناألصوات يسمع أن األصوات يمكنه يسمع أن يمكنه

ضغط فى تغيير تحدث ضغط التى فى تغيير تحدث التىيبلغ يبلغ الهواء PaPa 0.000020.00002الهواء

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فقد الهواء ضغط فى التغيير وحدات لصغر فقد ونظرا الهواء ضغط فى التغيير وحدات لصغر ونظراالديسيبل تسمى أكبر وحدة إستعمال الديسيبل تم تسمى أكبر وحدة إستعمال dBdBتم

. لوغاريتمية وحدة .وهى لوغاريتمية وحدة وهى

إلى باسكال من الضوضاء وحدات إلى ولتحويل باسكال من الضوضاء وحدات ولتحويل: األتية المعادلة إستخدام يتم :ديسيبل األتية المعادلة إستخدام يتم ديسيبل

dB = 20 log {sound pressure/Ref. Pressure (0.00002 dB = 20 log {sound pressure/Ref. Pressure (0.00002 Pa)}Pa)}

Sound pressure level in very quite room where the Sound pressure level in very quite room where the sound pressure is 0.002 Pa is:sound pressure is 0.002 Pa is:

Lp (dB) = 20 log (0.002/0.00002) = 20 log 100 = 40 dBLp (dB) = 20 log (0.002/0.00002) = 20 log 100 = 40 dB

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Common SoundsCommon Sounds0 dB Threshold of Hearing

30 dB Soft Whisper

40 dB Quiet Office

60 dB Conversational Speech

80 dB Very noisy restaurant

90 dB Subway

110 dB Woodworking

120 dB Hydraulic press

140 dB Threshold of Pain – Jet plane

180 dB Rocket

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How do we Hear?How do we Hear?الصوت- 11 موجات تلتقط الخارجية الصوت- األذن موجات تلتقط الخارجية األذنإهتزازها- 22 فتسبب األذن طبلة بخبط الموجات إهتزازها- تقوم فتسبب األذن طبلة بخبط الموجات تقومالمطرقة- 33 خالل األذن طبلة من اإلهتزازات المطرقة- تنتقل خالل األذن طبلة من اإلهتزازات تنتقل

والركاب والركاب والسندان والسندانحيث- 44 الداخلية األذن إلى الذبذبات هذه تنتقل ذلك حيث- بعد الداخلية األذن إلى الذبذبات هذه تنتقل ذلك بعد

تنقل التى الدقيقة الشعيرات ماليين وبها الكوكيالة تنقل توجد التى الدقيقة الشعيرات ماليين وبها الكوكيالة توجدنسمع وبالتالى المخ إلى نبضات شكل على الذبذبات نسمع هذه وبالتالى المخ إلى نبضات شكل على الذبذبات هذه

الصوتالصوت

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ExampleExample

In the field, we determined the loudness of In the field, we determined the loudness of two compressors right next to each othertwo compressors right next to each other

How loud is this area?How loud is this area?– Do we add?Do we add?– Do we add and take the average?Do we add and take the average?

89 dB 87 dB

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Neither, because it is a log scaleNeither, because it is a log scaleWe use the following chartWe use the following chart

82 dB + 83 dB = 86 dB82 dB + 83 dB = 86 dB87 dB + 89 dB = 91 dB87 dB + 89 dB = 91 dB

Difference in dB Values

Add to Higher Level

0-1 dB 3 dB

2-3 dB 2 dB

4-9 dB 1 dB

10 dB or more 0 dB

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How does the Safety How does the Safety Person determine noise Person determine noise levelslevelsSound level meterSound level meter

– Determine the Determine the loudness (dB) of loudness (dB) of noise at any given noise at any given

momentmomentالضوضاء قياس الضوضاء يتم قياس يتم

بواسطة بواسطة بالمنطقة بالمنطقةقياس قياس جهاز جهاز

الضوضاء الضوضاء مستوى مستوىلحظى يكون لحظى القياس يكون القياس

Personal DosimetersPersonal Dosimeters– Worn by employeesWorn by employees– Measures the average Measures the average

loudness in an 8 hour loudness in an 8 hour work shift work shift ““8hr. TWA”8hr. TWA” (Time (Time Weighted Average)Weighted Average)

بواسطة – القياس بواسطة يتم القياس يتمالدوزيميترالدوزيميتر

خالل – يكون خالل القياس يكون 88القياسمتوسط متوسط ساعات ساعات

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What does OSHA say?What does OSHA say?At 85 dB (8hr. TWA) (Action level)At 85 dB (8hr. TWA) (Action level)

الضوضاء تبلغ الضوضاء عندما تبلغ 88ديسيبل (ديسيبل (8585عندما ( هو هذا يعتبر ساعات ) متوسط هو هذا يعتبر ساعات متوسط

فيه قرار إتخاذ الواجب فيه الحد قرار إتخاذ الواجب الحد– Train employeesTrain employees

– Make hearing protection availableMake hearing protection available

– Sample for noise levelsSample for noise levels

– Do hearing testsDo hearing tests

– Notify employees of resultsNotify employees of results

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Hearing Conservation Hearing Conservation ProgramProgram

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Hearing Conservation Hearing Conservation ProgramProgram

Monitoring:Monitoring:

Employers should monitor noise exposure Employers should monitor noise exposure levels to identify employees who are levels to identify employees who are exposed to noise levels at or above 85 exposed to noise levels at or above 85 dBA averaged over 8 working hours, or dBA averaged over 8 working hours, or an 8-hour time-weighted average (TWA).an 8-hour time-weighted average (TWA).

Noise level meters & Noise Dosemeter are Noise level meters & Noise Dosemeter are used after being calibrated.used after being calibrated.

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When the daily noise exposure has two or more When the daily noise exposure has two or more noise exposures at different levels, their noise exposures at different levels, their combined values should be considered. (Use the combined values should be considered. (Use the following formula)following formula)

F(e) = (T(1) divided by L(1) + (T(2) divided by F(e) = (T(1) divided by L(1) + (T(2) divided by L(2)) + ……… (T(n) divided by L(n))L(2)) + ……… (T(n) divided by L(n))

F(e)= The equivalent noise exposure factorF(e)= The equivalent noise exposure factorT= The period of noise exposure at any essentially T= The period of noise exposure at any essentially

constant level.constant level.L= The duration of the permissible noise L= The duration of the permissible noise

exposure at the constant level.exposure at the constant level.If the value of F(e) exceeds unity (the value 1), the If the value of F(e) exceeds unity (the value 1), the

exposure exceeds PEL.exposure exceeds PEL.

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Example:Example:

110 dbA 0.25 hours110 dbA 0.25 hours

100 dbA 0.5 hours100 dbA 0.5 hours

9090 dbA 1.5 HoursdbA 1.5 Hours

F(e) = (0.25/0.5) + F(e) = (0.25/0.5) + (0.5/2)+(1.5/8)(0.5/2)+(1.5/8)

F(e)=0.5+0.25+0.1888F(e)=0.5+0.25+0.1888

F(e) = 0.938F(e) = 0.938

Since F(e) does not exceed Since F(e) does not exceed unity (1), the exposure unity (1), the exposure limit is within limit is within permissible limitspermissible limits

Duration Per Day, Hours

Sound Level dBA

8 90

6 92

4 95

3 97

2 100

1½ 102

1 105

¾ 107

½ 110

¼ 115

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Audiometric TestingAudiometric Testing

• Should the noise level monitoring determine Should the noise level monitoring determine that employees are being subjected to levels that employees are being subjected to levels equaling or exceeding a TWA of 85 dBA, the equaling or exceeding a TWA of 85 dBA, the next step is to establish an audiometric testing next step is to establish an audiometric testing program for those exposed at no cost to the program for those exposed at no cost to the employee.employee.

• The important elements of an audiometric The important elements of an audiometric program include: Baseline audiograms, Annual program include: Baseline audiograms, Annual audiograms, Control measures, Training, and audiograms, Control measures, Training, and follow-up procedures.follow-up procedures.

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Baseline AudiogramsBaseline Audiograms•It is the reference audiogram It is the reference audiogram against which future audiograms against which future audiograms are are compared.compared.•Must be provided within 6 Must be provided within 6 months of an employee’s first months of an employee’s first exposure at or above 8-hour TWA exposure at or above 8-hour TWA of 85 dBA. (Control measures of 85 dBA. (Control measures should be taken)should be taken)•Baseline Audiogram must be Baseline Audiogram must be preceded by 14 hours without preceded by 14 hours without exposure to workplace noise.exposure to workplace noise.

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Annual AudiogramsAnnual Audiograms

• After baseline audiogram has been taken, After baseline audiogram has been taken, each employee exposed to noise levels at each employee exposed to noise levels at the 85 dBA or above shall have annual the 85 dBA or above shall have annual examination.examination.

• Annual audiogram must be conducted Annual audiogram must be conducted within 1 year of the baseline.within 1 year of the baseline.

• Compared with baseline audiograms Compared with baseline audiograms results.results.

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ContinuedContinued

• To determine whether an employee has To determine whether an employee has experienced any recordable hearing loss.experienced any recordable hearing loss.

• The hearing loss is reffered to in the The hearing loss is reffered to in the OSHA standard as :OSHA standard as :Standard Threshold Standard Threshold Shift (STS).Shift (STS).

• OSHA defines STS as “a change in OSHA defines STS as “a change in hearing threshold relative to the baseline hearing threshold relative to the baseline audiogram of an average of 10 dB or audiogram of an average of 10 dB or more at 2000, 3000, and 4000, Hz in more at 2000, 3000, and 4000, Hz in either ear.either ear.

Example Baseline Example Baseline AudiogramAudiogram

125 250 500 1K 2K 3K 4K 6K 8K

10

0

10

20

30

40

50

Baseline Audiogram(The initial audiogram taken by worker when first employed.)

Annual Audiogram Annual Audiogram (Showing STS)(Showing STS)

125 250 500 1K 2K 3K 4K 6K 8K

10

0

10

20

30

40

50

BASELINE

ANNUAL

16 9

816 + 9 + 8 = 3333 / 3 = 11

Reportable Loss? NOSTS ? YES

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ControlControl

• The standard states that if the 90 dB PEL The standard states that if the 90 dB PEL is being exceeded, “feasible is being exceeded, “feasible administrative or engineering controls administrative or engineering controls shall be utilized.shall be utilized.

• If fails, PPE shall be provided and used If fails, PPE shall be provided and used to reduce sound levels.to reduce sound levels.

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Administrative ControlsAdministrative Controls

* Are defined as, “Methods of controlling * Are defined as, “Methods of controlling employee exposures by job rotation, employee exposures by job rotation, work assignment, or time periods away work assignment, or time periods away from the hazards.from the hazards.

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Engineering ControlEngineering Control

• Are defined as “ Methods of controlling Are defined as “ Methods of controlling employee exposures by modifying the employee exposures by modifying the source or reducing the quantity of source or reducing the quantity of contaminants released into the workroom contaminants released into the workroom environment.environment.

• Example: installing noise – absorbing Example: installing noise – absorbing acoustical foam or baffles to capture and acoustical foam or baffles to capture and deaden reverberating noise.deaden reverberating noise.

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Hearing ProtectorsHearing Protectors

• Hearing protectors shall be made Hearing protectors shall be made available and shall be worn by all available and shall be worn by all employees exposed to an 8-hour TWA of employees exposed to an 8-hour TWA of 85 dBA or greaters.85 dBA or greaters.

• Types of hearing protectors:Types of hearing protectors:

• Ear muffsEar muffs

• Ear plugsEar plugs

• Ear canalEar canal

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Earmuffs Earplugs Canal Caps

Examples of Hearing ProtectorsExamples of Hearing Protectors

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Hearing ProtectionHearing ProtectionNRRNRR - Noise reduction rating- Noise reduction rating

– Express - 25 NRRExpress - 25 NRR– Classic - 29 NRRClassic - 29 NRR– Max Lite - 30 NRRMax Lite - 30 NRR

DO NOT DO NOT Subtract the NRR from the Subtract the NRR from the noise levelnoise level– WRONG WRONG (109 dB - 25 NRR = 84 dB) (109 dB - 25 NRR = 84 dB)

You must use the You must use the “Safety Factor”“Safety Factor”

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Safety FactorSafety FactorOSHA says the hearing protection is OSHA says the hearing protection is

designed to reduce the noise by the designed to reduce the noise by the NRR, but that is unlikely to happen NRR, but that is unlikely to happen due to :due to :– Leaks in the sealLeaks in the seal– VibrationVibration– Improper insertionImproper insertion

(NRR - 7) (NRR - 7)

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Example of NRR Example of NRR ProtectionProtection

The noise at a large compressor is The noise at a large compressor is 109 dB109 dB

You are wearing the Express plugs with You are wearing the Express plugs with an an NRR of 25NRR of 25

Do you have enough protection to place Do you have enough protection to place you below 90 dB level?you below 90 dB level?

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Training - RecordkeepingTraining - Recordkeeping

• Employees training is very important. All Employees training is very important. All employees exposed to noise at a TWA of employees exposed to noise at a TWA of 85 dBA or greater shall participate in a 85 dBA or greater shall participate in a hearing conservation training program.hearing conservation training program.

• An accurate records shall maintained of An accurate records shall maintained of all employee exposure measurements.all employee exposure measurements.