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HEARING CONSERVATION

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Noise is generally defined as unwanted sound, we are all exposed to ... Inside the Cochlea (snail shell) Delicate hair cells vibrate to different frequencies ... – PowerPoint PPT presentation

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Title: 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

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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.

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  • 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.

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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.

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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.

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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

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