Hearing Conservation

1. Hearing Conservation 29 CFR 1910.95 برنامج الحفاظ على القوى السمعية Created By: C. Miterko

2. Sound is what we hear and is produced by vibrating objects and reaches the listener’s ears as waves in the air or other media. When an object vibrates it causes slight changes in air pressure. These air pressure changes travel as waves through the air and produce sound. الصوت ينتج من إهتزاز الأشياء ويكون على هيئة موجات تصل إلى الأذن. عندما تهتز الأشياء يحدث نتيجة لذلك تغيير بسيط فى ضغط الهواء. وهذا التغيير فى ضغط الهواء ينتقل فى الهواء على شكل موجات والتى بدورها تنتج الصوت What is Sound? ما هو الصوت

3. عندما يتم خبط الطبلة بواسطة العصاة ، يهتز سطح الطبلة وعندما يتحرك سطح الطبلة للأمام يحدث تغيير موجب فى ضغط الهواء وعندما يتحرك سطح الطبلة للوراء يحث تغيير سلبى فى ضغط الهواء وهكذا يتحرك هذا الضغط على شكل موجات حتى يصل للأذن ونسمع الصوت.

4. الضوضاء هى الأصوات غير المرغوب بها Hertz (Hz) يقاس بوحدة الهيرتز وهى عدد الذبذبات التى تنتج من تغيير ضغط الهواء فى الثانية الواحدة What is Noise?

5. Frequency • Humans can typically hear between 20 - 20,000 Hz • تسمع الأذن البشرية الأصوات بين 20 – 20000 هيرتز • التردد الخاص بالحديث العادى يكون فى حدود 3000 هيرتز • الإنسان ذو الصحة الجيدة يمكنه أن يسمع الأصوات التى تحدث تغيير فى ضغط الهواء يبلغ 0.00002 Pa

6. ونظرا لصغر وحدات التغيير فى ضغط الهواء فقد تم إستعمال وحدة أكبر تسمى الديسيبل dB وهى وحدة لوغاريتمية. • ولتحويل وحدات الضوضاء من باسكال إلى ديسيبل يتم إستخدام المعادلة الأتية: • dB = 20 log {sound pressure/Ref. Pressure (0.00002 Pa)} • Sound pressure level in very quite room where the sound pressure is 0.002 Pa is: • Lp (dB) = 20 log (0.002/0.00002) = 20 log 100 = 40 dB

7. Common Sounds

9. How do we Hear? • 1- الأذن الخارجية تلتقط موجات الصوت • 2- تقوم الموجات بخبط طبلة الأذن فتسبب إهتزازها • 3- تنتقل الإهتزازات من طبلة الأذن خلال المطرقة والسندان والركاب • 4- بعد ذلك تنتقل هذه الذبذبات إلى الأذن الداخلية حيث توجد الكوكيلاة وبها ملايين الشعيرات الدقيقة التى تنقل هذه الذبذبات على شكل نبضات إلى المخ وبالتالى نسمع الصوت

10. Example • In the field, we determined the loudness of two compressors right next to each other • How loud is this area? • Do we add? • Do we add and take the average? 89 dB 87 dB

11. Neither, because it is a log scale • We use the following chart • 82 dB + 83 dB = 86 dB • 87 dB + 89 dB = 91 dB

12. Sound level meter Determine the loudness (dB) of noise at any given moment يتم قياس الضوضاء بالمنطقة بواسطة جهاز قياس مستوى الضوضاء القياس يكون لحظى Personal Dosimeters Worn by employees Measures the average loudness in an 8 hour work shift “8hr. TWA” (Time Weighted Average) يتم القياس بواسطة الدوزيميتر القياس يكون خلال 8 ساعات متوسط How does the Safety Person determine noise levels

15. At 85 dB (8hr. TWA) (Action level) عندما تبلغ الضوضاء 85 ديسيبل (8 متوسط ساعات) يعتبر هذا هو الحد الواجب إتخاذ قرار فيه Train employees Make hearing protection available Sample for noise levels Do hearing tests Notify employees of results What does OSHA say?

17. Hearing Conservation Program

18. Hearing Conservation Program • Monitoring: • Employers should monitor noise exposure levels to identify employees who are exposed to noise levels at or above 85 dBA averaged over 8 working hours, or an 8-hour time-weighted average (TWA). • Noise level meters & Noise Dosemeter are used after being calibrated.

19. When the daily noise exposure has two or more noise exposures at different levels, their combined values should be considered. (Use the following formula) • F(e) = (T(1) divided by L(1) + (T(2) divided by L(2)) + ……… (T(n) divided by L(n)) • F(e)= The equivalent noise exposure factor • T= The period of noise exposure at any essentially constant level. • L= The duration of the permissible noise exposure at the constant level. • If the value of F(e) exceeds unity (the value 1), the exposure exceeds PEL.

20. 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 • Example: • 110 dbA 0.25 hours • 100 dbA 0.5 hours • dbA 1.5 Hours • F(e) = (0.25/0.5) + (0.5/2)+(1.5/8) • F(e)=0.5+0.25+0.1888 • F(e) = 0.938 • Since F(e) does not exceed unity (1), the exposure limit is within permissible limits

21. Audiometric Testing • Should the noise level monitoring determine that employees are being subjected to levels equaling or exceeding a TWA of 85 dBA, the next step is to establish an audiometric testing program for those exposed at no cost to the employee. • The important elements of an audiometric program include: Baseline audiograms, Annual audiograms, Control measures, Training, and follow-up procedures.

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

25. Annual Audiograms • After baseline audiogram has been taken, each employee exposed to noise levels at the 85 dBA or above shall have annual examination. • Annual audiogram must be conducted within 1 year of the baseline. • Compared with baseline audiograms results.

26. Continued • To determine whether an employee has experienced any recordable hearing loss. • The hearing loss is reffered to in the OSHA standard as :Standard Threshold Shift (STS). • OSHA defines STS as “a change in hearing threshold relative to the baseline audiogram of an average of 10 dB or more at 2000, 3000, and 4000, Hz in either ear.

27. Example Baseline Audiogram 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.)

28. Annual Audiogram (Showing STS) 125 250 500 1K 2K 3K 4K 6K 8K 10 0 10 20 30 40 50 BASELINE 16 9 8 16 + 9 + 8 = 33 33 / 3 = 11 Reportable Loss? NO STS ? YES ANNUAL

29. Control • The standard states that if the 90 dB PEL is being exceeded, “feasible administrative or engineering controls shall be utilized. • If fails, PPE shall be provided and used to reduce sound levels.

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

31. Engineering Control • Are defined as “ Methods of controlling employee exposures by modifying the source or reducing the quantity of contaminants released into the workroom environment. • Example: installing noise – absorbing acoustical foam or baffles to capture and deaden reverberating noise.

33. Hearing Protectors • Hearing protectors shall be made available and shall be worn by all employees exposed to an 8-hour TWA of 85 dBA or greaters. • Types of hearing protectors: • Ear muffs • Ear plugs • Ear canal

34. Examples of Hearing Protectors Earmuffs Earplugs Canal Caps

35. Hearing Protection • NRR- Noise reduction rating • Express - 25 NRR • Classic - 29 NRR • Max Lite - 30 NRR • DO NOT Subtract the NRR from the noise level • WRONG (109 dB - 25 NRR = 84 dB) • You must use the “Safety Factor”

36. Safety Factor • OSHA says the hearing protection is designed to reduce the noise by the NRR, but that is unlikely to happen due to : • Leaks in the seal • Vibration • Improper insertion • (NRR - 7)

37. Example of NRR Protection • The noise at a large compressor is 109 dB • You are wearing the Express plugs with an NRR of 25 • Do you have enough protection to place you below 90 dB level?

38. Training - Recordkeeping • Employees training is very important. All employees exposed to noise at a TWA of 85 dBA or greater shall participate in a hearing conservation training program. • An accurate records shall maintained of all employee exposure measurements.