Noise-Induced Hearing Loss 

and Hearing Conservation 

Session

Introduction to noise-induced 

hearing loss

R. J. Matetic

Mining Hearing Loss Prevention Workshop

June 21-22, 2005

Pittsburgh Research Laboratory
Why Noise is Bad for You

• It causes 

permanent

hearing loss

• It makes your ears ring

all the time
Miners Suffer Higher Rates of Hearing 

Impairment than Non-exposed Males

0

20

40

60

80

100

20 25 30 35 40 45 50 55 60 65

Age

Percent with hearing impairment

Metal/Nonmetal

Coal

Non-noise exposed

Impairment: > 25 decibel hearing loss (averaged over 4 frequencies in each ear)

Source: John Franks, NIOSH
Hearing Loss Types

• Conductive

– Outer and Middle Ear

– Usually low frequency, correctable

– Ex: earwax, hole in eardrum, head cold

• Sensori-neural

– Inner Ear

– Usually high frequency, not correctable

– Ex: aging, diseases, medications, noise
Noise damages “hair cells” in the 

inner ear

Cochlea

Healthy Damaged
This Is Your Ear...

Healthy

This Is Your Ear 

on Noise...

Damaged
Hearing is measured with 

an audiogram

Normal hearing

Below-normal hearing

-10

0

10

20

30

40

50

60

70

80

90

100

110

500 750 1000 1500 2000 3000 4000 6000 8000

Frequency (Hz) Hearing Level (dB)

-10

0

10

20

30

40

50

60

70

80

90

100

110

500 750 1000 1500 2000 3000 4000 6000 8000

Frequency (Hz) Hearing Level (dB)

Left

Right
Effect of loud [95dB(A)] 

noise over a career*

Start of career: Normal hearing

Lower limit

of normal

10 years

30 years

20 years

• Noise-induced loss 

greatest at 4000 Hz

• Some of this hearing 

loss is due to aging, 

but most is due to 

noise

-10

0

10

20

30

40

50

60

70

80

90

100

110

500 750 1000 1500 2000 3000 4000 6000 8000

Frequency (Hz)

Hearing Level (dB)

*(estimated based on ANSI S3.44 standard)
What workers tell us:

“My dad worked at [company] for thirty-something 

years and I hope I don’t end up like him. You got to 

scream for him to hear you.”

“It’s almost like you’re mad at yourself because why 

can he hear? He works in the same atmosphere; why 

can he hear and I can’t?”

“...machine backing up, beeping the safety alarm or 

something, you might not hear”

“...you can’t hear that little whistling noise, something that’s

a little bit out of the ordinary, it could be very dangerous.”

“It seems like new people...they’re the ones that might get 

hurt”

“Loss of hearing could put you or maybe your buddy 

in jeopardy if you don’t see something or hear 

something”
Where Hazardous Noise Comes 

From

• High-powered 

motorized equipment

• Striking, drilling, 

digging

• Air-powered tools
When is Loud TOO LOUD?

• Risk of damage starts at 85 

decibels (dB(A)) or higher

• Longer exposure times increases 

your risk

• Measure with instruments or....

• Look for warning signs

– Too loud for conversation 3’ away

– Everything sounds “dull”

– Ears “ring”
Typical Noise Levels

Heavy duty dozer

99 dB(A)

Light duty: 96dB(A)

Continuous 

mining 

machine

102 dB(A)

Air rotary drill rig 

(no cab)

99 dB(A)

Crawler crane

Over 35 ton, non-insulated cab: 97 dB(A)

Under 35 ton, non-insulated cab: 94 dB(A)

insulated cab: 84 dB(A)
What Can You Do About It?

More than you may think!

• First: Get rid of the noise

(Engineering controls)

• Second: Stay away from the noise

(administrative controls)

• Third: Protect yourself from the 

noise

(personal protective equipment)
First: Get rid of the 

noise

•“Engineering controls”

• Keep doors SHUT

–Reduces noise by 10-20 dB(A)

• Maintain cab seals

• Take care of mufflers and other 

controls

• Report worn or broken noise controls
Then: Stay away

from noise

• Have a hearing conservation 

program? Ask for list of 

“administrative controls”.

• Noisy and you don’t have to be 

there? Leave!

• Have a noisy task? 

Break it up!
Finally: Protect your ears:

• Noise high, but hearing protection low: 

For instance: only 48% of sand & gravel 

miners ever use it! (Deborah Landen, 2004)

• Find comfortable hearing protection

– Muffs, plugs, canal caps

• Learn to wear them correctly

• Practice listening through protection

– Hard, but easier than listening through 

damaged ears!

• Don’t go into noise without it!
For more information

R.J. Matetic

• Phone: 412-386-6560

• Fax: 412-386-4865

• rmatetic@cdc.gov

• Mining web:

www.cdc.gov/niosh/mining

• All industries:

www.cdc.gov/niosh/topics/noise

Pittsburgh Research Laboratory