Hearing Conservation

1. Hearing Conservation 29 CFR 1910.95 Created By: C. Miterko

2. Objectives • What is sound? • How the ear works • How to measure noise • What does OSHA says about noise? • Hearing Conservation Program • Reading hearing tests • Hearing Protection

3. Noise is generally defined as unwanted sound, we are all exposed to noise every day at home at work and in traffic. Hertz (Hz) Frequency a high or low pitch Decibels (dB) The loudness of the sound What is Noise?

4. Frequency • Humans can typically hear between 20 - 20,000 Hz • You can hear different frequencies better than others

5. Decibels • Sound pressure are measured in Decibels (dB) which is a logarithmic measure of sound pressure levels. • The quietest sound most humans can detect is 0 dB

7. Common Sounds

8. Anatomy of the Ear Semi-Circular Canals Ear Drum Cochlea Ear Bones

9. How do we Hear? • The outer ear collects the soundwaves • The waves hit the eardrum, and cause it to vibrate • The vibrations are sent through the ear bones to the cochlea

10. Inside the Cochlea (snail shell) • Delicate hair cells vibrate to different frequencies • Hair cells detect the vibration, and send a signal to the brain • Loud sounds destroy the hair cells, and they stop functioning FOREVER!

11. The Ear does something else too! • The Semi-circular canals • Three tubes laying perpendicular to one another • Filled with fluid and tiny hair cells • Depending on which way your head is tilted, the fluid moves the hair cells, and they send a signal to your brain • Responsible for balance

12. How to measure noise • Decibels are measured on a logarithmic scale • Every time you add 6 dB, you double the sound pressure of the noise

13. 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

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

15. Sound level meter Determine the loudness (dB) of noise at any given moment Personal Dosimeters Worn by employees Measures the average loudness in an 8 hour work shift “8hr. TWA” (Time Weighted Average) How does the Safety Person determine noise levels

16. At 85 dB (8hr. TWA) (Action level) Train employees Make hearing protection available Sample for noise levels Do hearing tests Notify employees of results What does OSHA say?

17. At 90 dB or more (100% Dose) We must keep levels at or below 90 dB Or require hearing protection that will lower noise levels to to 90 dB What does OSHA say?

18. 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 What are Our Noise Levels?

19. 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.

21. 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.

22. 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

23. 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.

25. 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.

26. 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.

27. 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.

29. Audiogram

30. 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.

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

32. 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.

39. 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

40. 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”

41. 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) / 2

42. 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?

43. Hearing Protectors

44. Ear Plugs

45. Ear muffs

46. 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.

47. A Final Note • Hearing is important • In time, noise levels at 85 dB can permanently damage your hearing • Wear your hearing protection both at work and at home • Choose hearing protection with a high NRR, and wear it properly