Transcript Noise CWU May11

Noise Measurement and
Control
CWU – May2, 2011
Eric E. Dickson, CIEC, CIAQC
Industrial Hygienist, ESD 101
(509) 789-3518
[email protected]
Noise – Irritating to Dangerous
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Purpose of Noise Measurement
Identify overexposed workers and quantify
their exposures.
Assess noise situation for engineering
controls
Assess background levels in audiometric
test rooms.
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Effects of Noise Exposure
• Our ears can recover from
short exposure to loud
noise, but over time nerve
damage will occur.
• The longer and louder the
noise, the greater chance
permanent damage will
occur.
• There is really no such
thing as “tough ears” or
“getting used to it”.
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Permanent effects of noise
Small “hearing hangovers” add up slowly
Hearing aids can’t fix hearing loss
This is
your ear...
This is your
ear on noise...
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Effects of Noise on Humans
Hearing loss
Dilation of the pupils
Secretion of thyroid hormone, adrenaline,
adrenaline cortex hormone
Heart palpitation
Movements of stomach and intestines
Muscle reaction
Constriction of the blood vessels
6
Allowable Exposure Times
The table below shows noise levels and how long a
person can be exposed without hearing protection
before there is damage to the ear.
Noise Level
Allowable Exposure Time
85 decibels
8 hours
90 decibels
4 hours
100 decibels
1 hour
105 decibels
30 minutes
110 decibels
15 minutes
115 decibels
0 minutes
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Types of Noise
Loudness
Whisper
Conversation/3 ft
Street sounds
Sander
Sporting event
Motorcycle riding
Concerts
Shooting range
10 decibels
60 decibels
70 decibels
85 decibels
100 decibels
112 decibels
125 decibels
130 decibels
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“Rock on”!!! …huh?
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Portable ear blasters – then and now!
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DOSH Permissible Exposure Limits
WAC 296-817 (DOSH)
8-Hour Time Weighted Average (TWA)
85 dBA
Maximum Level (sustained noise of > 1
second in duration) 115 dBA
Peak Level (impact/impulse noise of
< 1second in duration) 140 dBC
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Hearing Conservation Program
Required if worker 8-hour TWA is higher than 85
dBA
Mandatory audiometric testing
Make hearing protection available
Place warning signs in areas > 115 dBA
Record keeping
Employee access to records.
Engineering and/or Administrative controls
required if TWA > 90 dBA
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Hearing Protection Devices
Ear Muffs
Ear Plugs (disposable and reusable)
Custom-Molded Ear plugs
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Noise Reduction Rating (NRR)
Each hearing protection device has an NRR.
Usually range from 20-30dB.
Chose appropriate level of protection for the noise
exposure.
Too little protection won’t block out enough noise
Too much can block essential noises such as warning
alarms, etc.
Correction factor = NRR-7dB
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Instruments for Measuring Noise
Sound Level Meters
Measures noise at a given moment
Area monitoring – develop a “noise map”
May not reflect worker exposure
15
Sound Level Meter settings
‘Slow’ response time
‘A’ scale for continuous monitoring
‘C’ scale to measure impact/impulse noise
Range
Low: 35-100 dB
Hi: 65-130 dB
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Instruments for Measuring Noise
Dosimeters
Measure worker exposure for full work shift
• Assess compliance w/ noise standard
Calculates TWA, LAVG (average for actual
sample period), Maximum Levels, and Peak
Levels
Prints a chart w/ minute-to-minute noise levels
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Dosimetry Measurements
Place dosimeter at top of shoulder
Avoid windy days if outdoors
Measure all identified noise sources
Keep itinerary of tasks and equipment used
For retired claimants, chose person whose
job most closely matches the claimant
Same shift, equipment, routine if possible
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Dosimeter Settings & Standards
WAC 296-817
PEL: 85 dBA TWA
Weighting: ‘A’
Exchange (doubling) Rate: 5dB
Threshold: 80dB
Response: Slow
Ceiling: 115dBA (Max), 140 dBC (Peak)
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Noise Control
Three methods – in this order.
Engineering Controls
Administrative Controls
Personal Protective Equipment (PPE)
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Noise Control – Engineering (1st)
Control the source
Mufflers, soundproofing, enclosures, fan speed, etc.
Control the path
Sound absorbing materials on walls or ceilings
Barriers (walls, curtains, etc.)
Control receiver’s environment
Build sound booth, etc.
Move farther away from equipment
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Noise Control – Administrative (2nd)
Job rotation
Work process change
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Noise Control – PPE (last resort)
If you can’t reduce noise exposure by
Engineering or Administrative controls, the
last resort is to use Personal Protective
Equipment (PPE).
PPE should never be the first choice for a
permanent solution.
Ear muffs, ear plugs, etc.
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Your hearing is as fragile as an egg
shell. It can only be damaged once!!
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