HEARING CONSERVATION

1
Hearing Conservation
29 CFR 1910.95
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
What is Noise?

• 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

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

6
(No Transcript)
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
How does the Safety Person determine noise levels

• 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)

16
What does OSHA say?

• At 85 dB (8hr. TWA) (Action level)
• Train employees
• Make hearing protection available
• Sample for noise levels
• Do hearing tests
• Notify employees of results

17
What does OSHA say?

• 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

18
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.

20
(No Transcript)
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

• 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)0.50.250.1888
• 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.

24
(No Transcript)
25
Baseline Audiograms

• It is the reference audiogram against which
  future audiograms are compared.
• Must be provided within 6 months of an employees
  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.

28
(No Transcript)
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.

33
(No Transcript)
34
(No Transcript)
35
(No Transcript)
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
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

48
(No Transcript)