Noise and Hearing Conservation

Image credit: OSHA

0507

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

0507

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

0507

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

0507

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

0507

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

0507

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

0507

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

0507

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

0507

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

permanentImage Credit: OSHA

0507

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)

0507

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

0507

Evaluating the Noise Exposure Hazard• Conduct a noise

survey• Identify and characterize

high-noise sources• Identify impacted

employees

• Monitor impacted employees

• Repeat monitoringImage Credit: Tom Ouimet

0507

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?

0507

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

0507

Audiometric Exams• Exams can detect early signs of hearing

loss• Typically measures hearing threshold at six

frequencies• Hearing thresholds are compared with

previous audiograms

0507

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

0507

Has an STS Occurred?

Image Credit: Tom Ouimet

Baseline

Annual

0507

An Example of Hearing Loss in Carpenters

Image Credit: Tom Ouimet

0507

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

0507

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

0507

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

0507

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

0507

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

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

0507

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