Download MineNoise

Mine Safety and Health
Occupational Noise Exposure
SafetyWorks!
OBJECTIVES
• Background information on noise
• Review of regulation
• Identify the major requirements for a
hearing conservation program.
• Demonstrate the proper way to insert
or wear hearing protectors.
• Illustrate the preferred methods to
reduce noise.
YOUR EARS HAVE NO PROTECTION
Noise destroys your hearing little by little.
Exposure to noise occurs on and off the job.
Your ears typically “recover” from exposures to
low level noises.
However, permanent damage may occur from even a
single exposure to very loud noises.
Noise Effects Us In Other Ways
• Noise is Psychologically Stressful
• Noise may distract our attention and cause:
– Accidents, Misunderstandings, Poor Performance,
Fatigue and General Anxiety.
• NIOSH is studying the health effects of chemical
exposures (solvents) combined with excessive
noise exposures.
What is Noise?
• Energy
• Pressure changes in a medium (air) caused by
vibration or turbulence
• Pressure produces wave motion from source
• Amplitude = Loudness = Decibels = dB
60 dB = Average Speaking Voice
• Frequency = Cycles per Second = Hertz = Hz
1000 Hz = 1 Kilohertz = 1 kHz = Human Voice
How is Noise Measured?
• Noise is measured in decibels (dB) at a
certain scale, such as A or C.
• The decibel scale is logarithmic
• That means, with a 5dB exchange rate, 95 dB
is 100% more noise than 90 dB!
Human Hearing Ranges
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20 Hz (low rumble) to 20,000 Hz (whine)
Speech Between 500 Hz to 2000 Hz
Average Hearing Loss at 4000 Hz and up
0 dB (just audible) to 140 dB (causes pain)
80 dB(A) 8 hour TWA will effect some
100 dB(A) 8 hour TWA will effect all
Mine Safety and Health - Part 62
Occupational Noise Exposure
• Establishes the Permissible Exposure Limit
(PEL) of 90 dB(A) as an 8 hour time
weighted average (TWA)
• Mandates engineering or other controls (but
not ear protectors) to be used to reduce
noise levels to 90 dB(A) or below.
• Must assure that no miner is exposed to
sound levels exceeding 115 dB(A)
Mine Safety and Health - Part 62
Occupational Noise Exposure
• Administer a Hearing Conservation
Program (HCP) whenever the
8 Hour TWA = 85 dB(A) or greater!
• For Various Extended Workshifts, the
allowable noise exposure decreases.
Major Requirements of a HCP
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Exposure Monitoring
Employee Notification
Audiometric testing
Hearing Protectors
Employee Training
Recordkeeping
Monitoring
• Required where exposure may equal or
exceed 85 dB(A) as an 8 hr. TWA
• Measure 8 hr. TWA using:
– Calibrated type I or II integrating dosimeter
• Remonitor when change or new employee
• Employees may observe the monitoring
• Notify employees of monitoring results
Audiometric Testing
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Baseline test (within 6 months of exposure)
Annual audiograms (compared to baseline)
Performed by licensed audiologist or doctor
Inform employees in writing of results if:
– Abnormal test results
– Standard Threshold Shift (STS) detected
• In MSHA Form 7000-1 when average loss
>= 25 dB in either ear
Comparing Baseline and Annual
Audiograms
• Compare the latest audiogram with the oldest
• Compute differences of test results at : 2 kHz, 3
kHz and 4 kHz
• Notify employee within 10 days, of hearing loss
when > 10 dB(A), also known as a Standard
Threshold Shift (STS)
• Retrain employee on hearing protection
Audiogram Comparison for
Mr. I. Ben Listnen
Right Ear 500 1000 2000 3000 4000 6000
9/10/82
10
5
15
10
20
15
9/16/98
15
20
35
25
45
35
difference = 20
15
25
average = 20 + 15 + 25 / 3 = 60/3 = 20 dB
Standard Threshold Shift - YES
MSHA Recordable - NO
Hearing Protectors
• Noise Reduction Ratings (NRR) - adjust by
the following formula: (NRR-7)/2
• Foam Plugs:
– small, good in heat, least costly, good reduction
– maybe painful, spread infections or impact wax
• Ear Muffs:
– easy, visually observable, less infections
– less effective with glasses, hair or head motion
Demo
• With clean hands * insert a foam ear plug into one
of your ears and have your partner observe.
If you can not wear ear plugs or do not want to
participate with plugs, please do the exercise with
the ear muffs. Thanks!
* If you are not well today or have touched
someone who is not well, please wash your hands
before doing this exercise!
Employee Training
• Conduct annually on:
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Effects of noise on hearing
Reasons for annual audiograms
Proper selection, use and care of protectors
Pros and Cons of various protectors
• Other training may include:
– Explanation of audiometric test results
– Methods to control noise
Recordkeeping
• Required:
– Audiograms - Retain for duration of
employment, plus at least 6 months
• 62.171 ‘Audiometric test procedures’
• Recommended:
– Training dates/content/enrollment
– Personal/Area Monitoring Records
The Best Ways to Reduce Hearing
Loss (in order of priority)
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Eliminate the source
Substitute a quieter process
Engineer sound controls on the source
Isolate the source by distance
Shield the source
Provide sound dampening materials
Reduce exposure times
Hearing protective devices (last option)
Noise Controls
If > 100 dB You Must Reduce by 3 dB
• Acoustical Design
– Noise ~ Energy (HP) ~ 1x10 8 Velocity
– Energy can be Transmitted, Reflected or Absorbed
• Material rated by noise reduction coefficient (NRC)
• Closed Cell Foam / Air Gap / Sheet rock
• Optimal thickness = 1/4 wavelength
– Resonance
• RPM / Hz = resonant frequency
• Mufflers / Silencers / Reflection Chambers
• Active Cancellation Systems