noise and hearing conservation

Noise and Hearing Conservation

Image credit: OSHA

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Session ObjectivesYou will be able to:• Understand the effects of noise on hearing• Identify sources of noise in your workplace• Describe the purpose of audiometric testing

and be able to interpret your test results• Select, fit, and use hearing protection


What Is Sound?• Sound is a longitudinal pressure wave of

energy with the following characteristics:• Frequency (pitch) measured in hertz (Hz)• Pressure (loudness) measured in decibels (dB)

• Frequency and pressure of a sound wave with duration of exposure determine the risk of hearing loss


Noise Sources• Machinery, tools, and

equipment emit sounds of varying loudness and in particular frequencies

• Continuous or intermittent

• Low-frequency equipment noise sources cause hearing loss in the speech frequencies


Sound Pressure Levels ofCommon Noises Noise Source Loudness• Whisper 10 dB• Conversation 65 dB• Shop tools 90 dB• Pneumatic drill 100 dB• Woodworking shop 110 dB• Abrasive blasting 115 dB• Jackhammer 130 dB


OSHA Noise Exposure Limits• 90 dBA TWA for 8-hour exposure• 95 dBA TWA for 4-hour exposure• 100 dBA TWA for 2-hour exposure• 105 dBA TWA for 1-hour exposure• Use engineering controls, administrative

controls, and personal protective equipment (hearing protection) to meet standards


Indicators of High Noise Levels• Noisy conditions can make normal

conversation difficult• 80 dB–People have to speak very loudly• 85-90 dB–People have to shout• 95 dB–People have to move close together

to hear each other at all


How Is Noise Hazardous?• Noise can result in temporary or permanent

hearing loss• It can cause you to misunderstand

communication • It can cause you to miss important safety

warnings• It can create unhealthy stress


How We Hear Sounds• Sound waves enter the ear canal• Eardrum vibrations pass along tiny bones• Tiny hairlike cells flow back and forth• The auditory nerve sends signals to the

brain that are registered as sound


How Hearing Is Damaged• Hearing ability relies on

delicate parts that can be damaged in the inner and middle ear

• Hairlike cells in the inner ear are flattened by high noise levels and injured over time

• Hearing loss is gradual• Hearing damage is

permanent Image Credit: OSHA


Hearing Loss• Hearing loss is any

reduction in the ability to hear

• Two types of loss• Temporary hearing loss

(temporary threshold shift) may occur immediately following a high noise exposure

• Permanent hearing loss (standard threshold shift)


Signs of Hearing Loss• Difficulty hearing

people speak• Inability to hear certain

high-pitched or soft sounds

• Noise or ringing in ears• Getting complaints that

the radio or TV volume is too high

Image Credit: Tom Ouimet


Evaluating the Noise Exposure Hazard• Conduct a noise

survey• Identify and characterize

high-noise sources• Identify impacted

employees• Monitor impacted

employees • Repeat monitoring



Noise Hazards—Any Questions?• Any questions about the hazards of

excessive noise and how to identify them?• Questions about signs and symptoms of

hearing loss?• Questions about measuring hearing loss?


Elements of the Hearing Conservation Program• All employees exposed to >85 dBA for

8 hours must participate• You receive:

• Baseline and annual audiograms• Annual training on hearing loss• Audiograms and PPE

• Hearing protection is provided• Exposure assessment conducted

periodically


Audiometric Exams• Exams can detect early signs of hearing

loss• Typically measures hearing threshold at six

frequencies• Hearing thresholds are compared with

previous audiograms


Standard Threshold Shift (STS)• Hearing loss has occurred if you have

experienced a standard threshold shift (STS)

• Hearing ability changed by an average of 10 dB

• Revised hearing protection required for STS


Has an STS Occurred?


BaselineAnnual


An Example of Hearing Loss in Carpenters



Hearing Protection Use• Voluntary use if exposed to an 8-hour TWA

of 85-90 dB• Mandatory use when:

• Exposed to an 8-hour TWA of 90 dB• Exposed to an 8-hour TWA of 85 dB and have suffered an STS (hearing loss) or have not had a baseline hearing test


Hearing Protection Devices

Noise Reduction• Hearing protection devices must reduce

employee noise exposure below an 8-hour TWA of 90 dB

• Employees with STS, noise exposure reduced below an 8-hour TWA of 85 dB

• Noise reduction ratio (NRR)• Earplugs: use 1/3 of NRR• Earmuffs: use 1/2 of NRR


Hearing Protection Devices—Earplugs and Canal Caps • Must be properly

inserted to seal the ear canal• Slowly roll and compress

foam into cylinder• Insert into ear canal while

compressed• Keeps noise from

reaching the eardrum• Cotton is not an

earplug

Image Credit: State of WA-WISHA Services


Hearing Protection Devices—Earmuffs• Sealed against head

with ears fully enclosed• Hair out from muffs• Glasses and caps do

not interfere with seal• Headband adjusted so

cushions exert even pressure

• Cleaned with warm, soapy water and rinsed


Any Questions?• Any questions about audiometric testing?• Questions about our hearing protection

program?• About when to use hearing protection?• About hearing protection devices?


Key Things to Remember• Hearing is a very important sense – don’t

lose it• Noise exposure over 85 dB can cause

hearing loss• Hearing loss cannot be cured or repaired• Hearing tests are conducted annually and

can detect hearing loss• Hearing protection devices must be worn in

high-noise areas

noise and hearing conservation

Documents

all0507 business legal

noise surveyidentify

noise sourcesmachinery

effects of noise

noise exposure hazardconduct

hearing losshearing

permanent hearing lossit

hour exposure95 dba