1. Noise and Hearing Conservation
This session is part of the training required under our hearing Conservation Program. The
Occupational Safety and Health Administration (OSHA), requires a Hearing Conservation
Program whenever employees are exposed to noise levels that equal or exceed an 8-hour time-
weighted average sound level of 85 decibels.
TAKE HEARING PROTECTION SERIOUSLY!
Excessive noise can be a serious health and safety hazard and can cause the following:
 Fatigue from staining to hear or talk over loud noise
 Mental and physical stress
 Accidents, from inability to hear warnings
 Temporary or permanent loss of hearing
Follow these commonsense safety rules to protect your hearing:
 Wear approved hearing protectors
 Limit you exposure to loud noise (at work and at home)
 Keep machinery and equipment well-maintained to reduce noise
 Report sources of excessive noise to a supervisor
 Have your hearing tested regularly

2. Training will cover:
 The impact of noise on your hearing
 Advantages and disadvantages of hearing protection devices
 The use, care and fit of hearing protection devices
 The need for hearing, or “audiometric”, tests and what to expect when you have these tests
 Training will be provided annually
Objectives:
 Understand the effects of noise on hearing
 Identify sources of potentially hazardous noise in the workplace
 Describe the purpose of audiometric testing and be able to interpret your test results
 Select, fit and use hearing protection
What is sound?
First, the basics. Sound is a longitudinal pressure wave of energy with two important
characteristics: frequency and pressure.
Frequency or pitch, is measured in hertz, or cycles per second. The human ear can
hear between a range of 20 to 20,000 hertz. The human voice is normally in the
range of 500 – 2,000 hertz.
Pressure is what determines the loudness of a sound, and it is measured in decibels.
A whisper is approximately 10 dB, while the noise of a chain saw is approximately
100 dB.
The frequency and pressure of a sound wave, together with the duration of exposure to this wave,
determine the risk of hearing loss and other noise hazards. The longer you are exposed to noise,
the greater your chance of hearing damage.
Noise sources:
 Machinery, tools and equipment emit sounds of varying loudness and in a particular range
of frequencies.
 Noise sources may be continuous, like most machines, or they may be intermittent, like a
punch press or a jackhammer.
 Low frequency noise sources such as vibrating equipment are particularly hazardous. They
can cause hearing loss in speech frequencies (meaning your ears can lose their ability to
hear what other people are saying).

3. Sound pressure levels of common noises:
NOISE SOURCE LOUDNESS
WHISPER 10DB
CONVERSATION 65 DB
SHOP TOOLS 90 DB
PNEUMATIC DRILL 100 DB
WOODWORKING SHOP 110 DB
ABRASIVE BLASTING 115 DB
JACKHAMMER 130 DB
You risk hearing damage when you are exposed to more than about 90 decibels over an 8-hour
period without hearing protection. A sound level of 14 decibels for any length of time is
considered to be very dangerous to your hearing. Note from the list, how many common
workplace noise sources are more than 90 decibels.
OSHA noise exposure limits
OSHA requires different exposure limits, depending on the loudness of the sound; the louder the
noise, the less time for exposure is permitted. When these limits are reached, we try to reduced
exposure to noise by using engineering and administrative controls. Hearing protection is used if
these controls are not effective or cannot be put into place.
*TWA= Time-weighted Average *dB= Decibels
90 DB TWA 8-HOUR EXPOSURE
95 DB TWA 4-HOUR EXPOSURE
100 DB TWA 2-HOUR EXPOSURE
105 DB TWA 1-HOUR EXPOSURE
Indicators of high noise levels
You can generally tell when noise levels are close to or go beyond permissible exposure limits.
Noisy conditions make normal conversation difficult or impossible.
 At 80 decibels, people have to speak very loud to be heard

4.  At 85 to 90 decibels, people need to shout in order to be understood
 At 95 decibels, people have to move very close together in order to be able to hear each
other at all
How is noise hazardous?
Noise can cause temporary or permanent hearing loss. It can cause you to misunderstand
communication with co-workers. This could cause you to do something that causes an accident.
Similarly, noise can cause you to miss important safety warnings, like if a co-worker tries to warn
you of a nearby hazard. Finally, noise creates stress that can affect you both physically and
mentally.
How we hear sounds
To understand how noise can be harmful, we first need to understand how we hear sound.
1. Sound waves enter the ear canal and travel until they strike the eardrum.
2. The vibrations of the eardrum are passed along by tiny bones (sometimes referred to as
the hammer, anvil and stirrup), into the inner ear.
3. The vibrations cause tiny hair-like cells in the inner ear to move back and forth, similar to
a field of glass being moved by a gust of wind.
4. The moving cells stimulate the auditory nerve that sends a “sound” signal to your brain.
How hearing is damaged
Our ability to hear depends on small, delicate parts in the middle ear or inner ear, especially the
hair-like cells in the inner ear. When functioning normally, these cells like flat when exposed to
loud noise. When the noise stops, the cells spring back. But, over a long period of exposure to
loud noise, the cells take longer to spring back until they eventually are too damaged to return to
their normal position. People who say that noise does not bother them may in fact be losing their
hearing function so noise does not seem as loud.
Hearing loss is gradual and most often is caused by long-term damage to the cells in the inner ear.
Once hearing damage happens, it is usually permanent and cannot be regained.
Hearing loss
Hearing loss is any reduction in your ability to hear sounds, compared to a person with normal
hearing who is about your same age.
Two types of hearing loss:
1. Temporary hearing loss (known as temporary threshold shift), may occur
immediately following exposure to a very loud nose. In this type of hearing
loss, because the damage to the ear is only temporary, the ability to hear
normally is restored after a few hours.

5. 2. Permanent hearing loss (known as standard threshold shift), is the result of
permanent damage to the inner ear. This type of hearing loss cannot be
restored.
Sings of hearing loss
Sings of hearing loss are often difficult to notice because hearing loss is usually very gradual and is
not painful. Here are some of the signs that you should be alert to:
 Difficulty in hearing people speak. Do you find yourself asking people to speak up or to
repeat what they have said because you could not hear them?
 Inability to hear certain high-pitched or soft sounds. You may have trouble hearing the
ticking of the clock or a watch.
 Noise or ringing in one or both ears.
 Getting complaints from others that the volume of the radio or TV is too high.
Evaluating the noise exposure hazard
To know whether there is a risk of hearing damage in the workplace, we must first evaluate the
noise exposure to see if it is hazardous.
The first step is to conduct a noise survey. This identifies and characterizes sources of high noise
and identifies employees who may be impacted by high noise levels. Next, we monitor the noise
exposure of employees who may be impacted. Typically, a “noise dosimeter” is used. The
dosimeter records all noise levels and computes the average noise exposure for each employee.
The readings from one employee may be also used for other employees who have similar jobs.
Finally, we repeat the noise monitoring whenever there is a change in production, process, or
equipment that may change noise levels.
It is important for your safety that you understand how excessive noise can affect your hearing
and the symptoms of hearing loss.
Audiometric exams
Audiometric exams, or audiograms, can detect early signs of hearing loss. An audiometric exam
typically measures hearing ability in each ear and finds your threshold for hearing six different
sound frequencies (500 , 1,000, 2,000, 3,000, 4,000, and 6,000 hertz).
These hearing thresholds can be compared with previous audiograms to determine if there has
been a “threshold shift” or a loss of hearing at any of the frequencies.
Hearing protection use
To protect against hearing loss, the use of hearing protection is required by OSHA under different
conditions of noise exposure. Hearing protection us is voluntary for employees who are exposed
to an 8-hour time weighted average of 85 to 90 decibels. Use of hearing protection becomes
mandatory at no cost to the employees when:

6. 1. There is exposure to an 8-hour time weighted average of 90 decibels or higher
2. There is exposure to an 8-hour time weighted average of 85 decibels when a standard
threshold shift (STS), or hearing loss, has already been measured or if a baseline hearing
test has not yet been conducted.
Hearing protection devices noise reduction
Hearing protection devices reduce your exposure to noise. Devices are expected to achieve the
following:
 Hearing protection devices must reduce noise level exposure to below an 8-hour time
weighted average of 90 decibels.
 For employees who have suffered an STS, hearing protection must reduce exposure to less
than an 8-hour TWA of 85 decibels.
 The noise reduction ration, or “NRR”, is the number of decibels that different types of
hearing protection devices are rated to reduce noise exposure. However, the NRR is only
what is achieved through laboratory testing rather than real-world applications.
Therefore, you should assume that the rea-world NRR of hearing protection device will be
significantly less than what may be shown on the package, due to such variables as poor fit
or incorrect use.
*Always wear your hearing protection when you are
in noisy locations.
Hearing protection devices – Ear plugs and canal caps & earmuffs
Two of the most commonly used hearing protection devices are earplugs and canal caps. There
are many different brands of earplugs, but they all work in a similar way. Typically, you roll or
compress the foam plug into a cylinder, insert it in your ear, and allow the foam to expand and fill
the ear canal. Earplugs are effective protection against noise and are lightweight and unobtrusive.

7. Make sure that the plugs are clean before inserting them in your ear. You should get a new pair of
earplugs each day or more frequently than necessary.
Canal caps can be useful if you are exposed to loud noise for short periods of time, or if you need
to walk through a noisy area to get from one place to another. Canal caps usually do not provide
the same degree of protection as earplugs because they do not enter the ear canal.
Cotton balls are not effective as hearing protection and should not be used.
Earmuffs are hearing protection devices that are usually used in conjunction with earplugs to
reduce noise exposure even further. However, they must fit correctly and form a good seal, or
they might actually increase noise exposure by creating an echo effect inside the earpiece. Note
that headphones from radios or CD players do not count as earmuffs or hearing protection
devices.
*Note: Headphones from radios or CD players do not count as earmuffs or hearing
protection devices.
Guidelines for earmuffs:
 The muffs must be sealed against the head and fully enclose the ears
 Hair should be pulled out and away from earmuffs
 Glasses and caps should not interfere with the seal
 The headband should be adjusted so that the cushions exert even pressure
 Earmuffs should be cleaned periodically with warm, soapy water and rinsed thoroughly
KEY FACTORS TO REMEMBER
 Your hearing is a very important sense – do not lose it
 Noise exposure of 85 decibels or more can cause hearing loss
 Hearing loss cannot be cured or repaired
 Hearing tests that are conducted annually can detect hearing loss so that steps can be
taken to prevent further hearing loss
 Hearing protection devices should be worn in high-noise areas