Measuring Noise
Noise hazard depends on the level
(sometimes called intensity) of the noise,
its duration, and how often the exposure
occurs. The point above which regular
exposure to sounds becomes hazardous is
a level of about 85 decibels (abbreviated
dB, or sometimes dBA which is the value
that more closely corresponds to human
hearing). Noise is measured using a sound
level meter.
The Sound Around Us
Noise is everywhere. It is the most pervasive environmental pollutant on the
planet. Virtually everything we do makes noise, and the more we do it, the faster
we do it, and the more of us there are - the more noise is made. In fact, silence, by
which we mean complete absolute quiet, is so rare that few of us have had the joy,
or perhaps even the possibility to experience it. If we have, it is so unusual that we
can likely cite the time and place of its last occurrence. The opportunities to savor
such tranquility are rapidly vanishing.
Not only is noise present in our daily routines and recreational activities,
but upwards of 5 million Americans, possibly as many as 30 million, work in
hazardous noise on a daily basis. Estimates from the National Institutes of Health
suggest that hearing loss afflicts 28 million Americans. About 1/3 of those cases
are at least partially attributable to noise. Later in this booklet we’ll tell you how
the ear works and how noise can affect it, so you will understand why you should
protect your ears from too much sound today in order for your hearing to serve
you tomorrow.
In a world as noisy as ours we frequently tune out. Moreover, our culture is so
visually dominant that often sight overwhelms the other senses such as audition
(the hearing of sounds), which is habitually relegated to second-class status. The
purpose of this pamphlet is to address these issues – to increase your appreciation
and awareness of the sounds around you and to provide some tools to help you
protect yourselves from loud, annoying and/or hazardous sound.
You Don’t Get “Used to Noise”
Noise does not have to be uncomfortably
loud, or even painful, to be damaging. You
may think your ears are “used to the noise,”
but what has probably happened is that your hearing has been temporarily dulled or that hearing loss has already begun.
A Rule of Thumb
When you feel the need to shout in order
to be heard three feet away, the noise levels
are probably 85 dBA or more and hearing
protectors are recommended.
Using Your Ears to Assess
Noise Risk
If, after the noise stops, you notice a ringing,
buzzing, or whistling in your ears that wasn’t
there before, this is a warning indicator.
Called tinnitus, this is like a “sunburn”
of the nerve cells of your inner ear,
indicating that they have been irritated and
overworked. Tinnitus is especially noticeable
in a quiet place, such as when you are trying
to go to sleep at night. If you don’t protect
your ears from noise, tinnitus can become a
permanent, constant annoyance in your life.
Apparent muffling or softening of sounds
after noise exposure is a warning sign that
your hearing is affected by a temporary
threshold shift. Repeatedly exposing your
ears without protection can cause the shift to
worsen and become permanent, resulting in
untreatable damage to your hearing ability.
Pain threshold
Jet Takeoff
Dual protection may be needed
Basketball
Game
Crowd Noise
Large
Stamping
Press
Chain Saw
Drilling Concrete
Leaf Blower
Vacuum
Cleaner
Inside MidSize Auto
(65 mph)
Short exposures
can cause permanent hearing loss
Prolonged exposure
causes moderate to
severe loss. Wear
hearing protectors
with extra care
Prolonged exposure
causes mild to
moderate loss.
Hearing protectors
required
Prolonged exposure
causes slight
hearing loss.
Hearing protectors
recommended
Conversation
Residential boundary-noise
limit
Floor Fan
Quiet Library
Rice Krispies
Sleep disruption
may begin
Watch
Ticking
Quiet
Wilderness
(no wind)
Threshold of
Hearing
Hearing Protection
Earplug Fitting Tip
Hearing loss due to noise is almost entirely preventable by judicious use of hearing
plugs the noise levels should be about the same whether or not the ears are covered.
protection. To find what is best for you, try different devices from the wide variety
available today. Be sure to carefully read the instructions because hearing protectors
must fit properly and be worn correctly to do the job. Hearing protector effectiveness
is specified by a Noise Reduction Rating (NRR), typically ranging from 15‑35
decibels. In practice the protection that normally can be achieved is about 10‑20
decibels. The more carefully you fit and wear hearing protectors, the higher your
protection will be. Hearing protectors may feel uncomfortable at first, but give yourself
a chance to get used to them, just as you do with a new pair of shoes or glasses.
Foam plugs, made from expandable slow-recovery
foam, provide the best combination of comfort
and protection for most users. They must be properly
prepared for insertion. One size fits most. Once in the
ear, foam plugs expand to provide a snug and secure
custom fit. The two most common complaints about
foam plugs (“not enough protection,” and “they don’t
stay in”) are almost always solved by greater practice
and care in insertion.
Premolded plugs are made from flexible materials
that are preformed to fit the ear. They are generally
available with a joining cord to prevent loss. Although
the version pictured at the left is a one-sized product,
many premolded plugs are sold in two or more sizes
and must be individually sized for each ear. If after
a period of regular wear you’ve been unable to get
used to your earplugs, try another size, type, or brand
of hearing protector.
Press firmly cupped hands over your ears while listening to a steady noise. With properly fitted
How Much Protection
Don’t get hung up on the NRR, the government-mandated noise protection factor that appears
on all hearing protector packaging. The numbers are based on optimized laboratory tests that, in
practice, represent what only a few of the most-motivated best-trained users can achieve. Your
best bet is to use the NRR only as an indicator that a product was designed and tested for noise
reduction. Except for very loud noises such as gunfire where selection is more critical, most
hearing protectors provide sufficient protection when worn properly and consistently. Foam
plugs or earmuffs, or a combination of the two generally provide the highest levels of protection.
Slowly roll and
compress foam
plugs into a very
thin crease-free
cylinder. While
compressed,
insert plug well
into the earcanal.
Fitting is easier if you
reach around the head
to pull the ear outward and
upward during insertion.
Keep the plugs clean
and free from material
that can irritate the
earcanal. They may
be washed in mild
liquid detergent and
warm water. Squeeze
excess water from the
plugs and allow to fully
air dry. Washing may be
repeated several times. Discard
plugs if they noticeably change their firmness or
do not re-expand to their original size and shape.
Reach around the
back of your head
and pull outward
and upward on
the ear while
inserting the
plug until you
feel it sealing.
This may seem tight
at first, especially if
you’ve never worn earplugs.
Carefully twist the plug to break the seal for a
slow, safe removal.
Premolded plugs will
normally last several
months or more
depending upon
the type, and
environmental
factors. They should
be replaced if they
shrink or swell, harden
or soften, tear, crack, or
become permanently deformed.
Wash them in warm soapy water and rinse well.
When dry, store them in a carrying case.
Hearing Protection
Hearing Protector Fitting Tip
Initially you may be concerned that you’ll be unable to hear while wearing protection.
becoming deeper, hollow, or muffled due to what is called the occlusion effect. If you don’t
However, unless you already have a significant hearing loss you’ll be surprised how
hear the change, or if it isn’t the same in both ears, you have not obtained a proper fit and
well you can hear speech and many other sounds while protected in the noise.
acoustic seal in either one or both ears.
When either a plug or muff is properly fitted, the sound of your own voice should change,
When you properly wear hearing protectors you’ll be protected from temporary
hearing shifts so that you are able to hear as well after a noise exposure as when it
Tip: Talking in Noise
started. People with hearing loss also benefit, since without protection noise will
When you wear plugs or muffs in noise you tend to speak less loudly than otherwise because
continue to damage their hearing until it is difficult to distinguish sounds under even
the protector makes your own voice seem louder and the surrounding noises seem quieter. So,
the best of conditions.
you have to speak up – speak more loudly than you think you need to. Others will appreciate
this, and your message will be better understood.
Semi-inserts, also called canal caps, consist of pods or
flexible tips on a lightweight headband. Because they are
quick to put on and take off and easy to store around
the neck, they are ideal for intermittent use. Those
that just cap the canal entrance give rise to a larger
occlusion effect (see above) which can be annoying to
some wearers.
Earmuffs have rigid cups with soft plastic cushions that
seal around the ears to block noise. Muffs come in
one-position or multi-position bands, and are also sold
in styles for attachment to hard hats. Cushions may be
filled with foam, liquid, or a combination; let personal
preference be your guide. For sustained exposures to very
loud noises, or if you feel the need for more protection,
wear muffs and plugs together (dual protection) for an
additional 5-10 dB of noise reduction.
Hold the large ends
of the pods and
swivel them to
direct the tips
into the earcanal
openings. Firmly
push and wiggle
the pods into the
canals until a snug
seal is obtained.
Pulling on the outer ear
while pushing on the pods will be helpful
to most wearers.
Most semi-inserts can be
cleaned in the same
way as premolded
earplugs. Since the
headband holds
the tips in place to
provide an acoustic
seal, don’t tamper
with it or the protection
the device provides
may be reduced. Many
manufacturers sell replacement tips.
Muffs must fully enclose
the ears to seal
against the head.
Adjust the headband so cushions
exert even pressure
around the ears to
get the best noise reduction. Pull hair back
and out from beneath the
cushions. Don’t store pencils or wear caps
under cushions. Thick or poorly fitting eyeglass temples may also cause some loss in noise reduction.
Cushions can be cleaned
with warm soapy water
and rinsed thoroughly.
Do not use alcohol or
solvents. Cushions
normally need
replacing at least
yearly, or whenever
they become stiff,
cracked, or no longer seal.
Don’t modify earmuffs in any
way, and especially do not stretch or abuse the
headbands as this will reduce your protection.
Specialized Hearing Protectors
Musician’s Earplugs
Certain earplugs are designed for moderate noise reduction and
better sound quality (more uniform attenuation across the range
of frequencies). For many sound exposures such as live music,
public events, and transportation, these devices provide the
needed protection, while making listening easier and more
enjoyable. The effect with these earplugs can be compared to
wearing medium neutral-gray sunglasses instead of very dark
color-tinted lenses that dramatically change one’s perception. The
Professional Musician E•A•R® Plug is one such product. Special types
of custom earmolds also provide this feature.
Your Hearing How it works and how we measure it
How We Hear
Healthy inner-ear nerves (hair cells) are the key to good hearing.
Although some die off naturally as you age, many more are killed
early if your ears aren’t protected from harmful noise.
Custom Molded Earplugs
Electronic Earmuffs
Some earmuffs use a microphone embedded in the earcup to pickup
sounds and transmit them through the earmuff to an earphone
inside. This allows better hearing at low sound levels without
the need to remove the device, while still providing sufficient
protection at higher sound levels. Typically the electronics in the
muff limit the amplified sound to a predetermined safe value such
as less than 85 dBA. These muffs can be excellent for use while
hunting or on the firing line, and for those with a mild hearing loss
they can actually amplify sounds, thus making it easier to hear.
Active Noise Reduction (ANR)
Today it is possible to use sound to cancel sound. A microphone within
the earmuff detects the sound passing through the cup walls and sends
that signal through circuitry to generate an anti-phase version that
is rebroadcast through a speaker in the cup. The result is sound
cancellation, but due to physical limitations this process only works
well in the lower frequencies, middle C and lower. This is effective
in certain military situations, and in general aviation, especially when
the devices also include communications. The principal consumer
application is reduction of nuisance noise such as experienced while
traveling. An ANR earmuff, which also plugs into an earphone jack
on entertainment devices, can provide balanced noise reduction while
simultaneously permitting listening to music or movies.
The outer ear collects and
funnels sound waves along
the earcanal to the eardrum.
The middle ear contains a
chain of three tiny bones, called
ossicles, which link the eardrum
to the inner ear. When sound
waves strike the eardrum, the
ossicles conduct the vibrations to
the cochlea in the inner ear.
Hair cells within
the cochlea of the
inner ear respond
to vibrations
by generating
nerve (electrical)
impulses. The
brain interprets
these as sound.
Measuring Hearing
Hearing is measured by a professional with an audiometer that sends tones to each ear
through earphones. You listen carefully and respond each time you hear a tone. The levels
at which you can barely hear the tones are your hearing threshold levels.
Your thresholds (measured in decibels) are recorded on a chart called an audiogram, for
tones at different pitches or frequencies (measured in “Hertz,” which is a special term
for cycles/second). Normal thresholds fall within the unshaded area on the chart. When
hearing loss occurs the thresholds fall into the shaded areas, meaning sounds must be
increased in level for you to hear them.
It is a good idea to have a complete hearing
evaluation even if you don’t suspect a
hearing problem. This gives you a baseline
against which to compare future audiograms
if problems occur. Professionals suggest
evaluations every 10 years; more often for
those over 50. If you anticipate regular
exposure to high-level noise, for example
if you are an avid recreational shooter, you
may wish to obtain more frequent tests
until you can assure that your hearing is
stable. Unusual changes would alert you
and your hearing specialist (audiologist or
otolaryngologist) to look for noise-related
(inadequate or improperly fitted protection)
or medical causes before it’s too late.
–10
HEARING THRESHOLD LEVEL, dB
Earplugs can be made by taking a custom impression of the earcanal
using a material with the consistency of thick honey. These can be
very comfortable and are suitable for use for hearing aids and
some specialized earplugs. However, for the simple purpose
of providing noise reduction, they offer little that other types
of earplugs cannot provide at a lower cost. Although they are
“customized,” their acoustic seal can be compromised because
they require a precise impression and must fit exactly. For
maximum protection, and equivalent and sometimes better comfort,
a foam earplug is usually preferred.
Degrees of hearing loss
Normal Hearing
0
10
20
SLIGHT
30
Hearing
Impairment
40
50
MODERATE
60
70
80
SEVERE
90
100
500
1000 2000 3000 4000 6000
FREQUENCY, HERTZ
high pitched
low pitched
sounds
sounds
Do Yourself a Favor Save Your Hearing!
Person-to-Person
Communication
Inarguably, the most important function
of our hearing is communication. A
person with hearing loss may not hear or
understand family members and friends,
particularly women and children with
high-pitched voices. Communication over
the telephone for business or pleasure
becomes more difficult. The individual
will confuse similar-sounding words
and mistake the message. Embarrassed
to ask the speaker to repeat, the listener
may just “tune out.” Conversing in groups
is most difficult, especially if there is
background noise. People with hearing loss
often become socially isolated as others find it too
much trouble to speak to them. What’s more, hearing aids can’t completely correct the problem
because louder sounds are not necessarily clearer to the damaged ear.
Often the message is as much in the sound of the voice as in the content of the speech. Poet
Maya Angelou has observed, “Words mean more than what is set down on paper. It takes the
human voice to infuse them with shades of deeper meaning.”
Effects of Age and Noise on Hearing
Hearing loss from the natural aging process causes a
gradual hearing decline, as shown in the figure to the
right. It affects mainly the ability to clearly hear highpitched sounds such as children’s voices, rustling leaves,
and some musical instruments.
Although age-effect hearing loss up through age
60 does not usually impair one’s ability to hear and
understand speech, problems occur when noiseinduced loss is added to age loss. The noise-induced
component can come from occupational exposures
as well as the many loud recreational sounds we
willingly expose our ears to on a daily basis. With noise
damage, even a 30-year-old can have trouble listening
in situations in which background sound is present,
such as in restaurants and other social situations.
Sounds You Want to Hear
A hearing-impaired person may not
be able to enjoy ordinary sounds of
nature or even the sounds of pets, and
distortion from damaged hair cells
may make music seem like “just a
racket.” It becomes difficult to detect
problems with tools or car engines by
listening for changes in the sounds
they make. It can be inconvenient to
miss the sound of the alarm on your
wristwatch or the phone ringing in the
next room. Hearing-impaired people
worry about getting hurt by missing
danger signals such as warning
beepers or smoke detectors.
Remember:
You Need Your Hearing!
These comments from people with
noise-induced hearing loss show why
it is worth the effort to wear hearing
protectors properly: your quality
of life depends on keeping your
good hearing. Once hearing is lost
it is gone forever. And if you aren’t
willing to wear an earplug for hearing
protection today, how would you
tolerate wearing a hearing aid that
fits to the ear with an earplug-like tip,
every day and every waking hour for
the rest of your life.
Even if you already have some
hearing loss, it is still essential to
wear hearing protectors from now on
to prevent the loss from worsening.
Carry them with you like a pair of
sunglasses so that whenever annoying
or potentially damaging sounds
assault your ears, you have the
protection you need. It’s never too
late to start conserving your hearing!
…Always this ringing in my ears.
My daughter no longer seems to
speak clearly.
I miss the birds, the wind in the
trees, the whispers.
I miss all the good sounds…
Noise Is All
Around
Be aware of noisy situations
such as the ones illustrated to
the right, so you can protect
yourself and enjoy a lifetime
of good hearing.
Gunshots
Protection is needed when shooting at both
indoor and outdoor ranges. For some people,
exposure to one unprotected shot can spell
permanent hearing loss.
Power Tools
Semi-insert devices or earmuffs can be
effective and convenient protection for these
intermittent exposures
Chain Saws & Leaf Blowers
Hearing protection is a must whenever operating
these very loud tools. Not only will you protect
your hearing, but you will feel more relaxed too.
Aircraft
When flying in small aircraft, foam earplugs or
other hearing protectors are suggested. Pilots
need protection too.
Where to Buy
Hardware stores and home centers,
pharmacies, sporting goods stores and
gun dealers, music stores, on the web
and industrial safety distributors.
Music
If it’s too loud, even music can be harmful to your
hearing. Keep a safe distance from loudspeakers
and if necessary, such as at concerts, wear
hearing protection.
Radio Headphones
For Additional Information
For additional discussion of hearing
and its protection, for product
information, or for an electronic copy
of this pamphlet go to: www.e-a-r.com/hearingconservation
Be smart – keep the music turned to safe levels.
As a rule of thumb, while listening to headphones
you should still be able to hear others speaking
to you from a few feet away.
Nuisance Noise
For these noises simply pick that plug or muff that is
comfortable for you. For snoring the plug of choice
will almost always be a foam plug for its combination
of great noise reduction and nightlong comfort.
WARNING!
Hearing protectors help reduce exposure to hazardous noise and other loud sounds. Misuse or failure to wear hearing protectors at all times that you are
exposed to hazardous noise may result in hearing loss or injury. For proper use, see user instructions, supervisor, or call 3M in U.S.A. at 1-800-243-4630.
In Canada, call Technical Service at 1-800-267-4414. If there is any drainage from your ear or you have an ear infection, consult with your physician before
wearing earplugs. Failure to do so may result in hearing loss or injury.
*Research suggests that many users will receive less noise reduction than indicated by the NRR due to variation in earplug fit and wearing time. It is
recommended that the NRR be reduced by 50% for estimating the average amount of noise reduction provided.
3M Occupational Health &
Environmental Safety Division
3M Center - Building 235-2W-70
Saint Paul, MN 55144-1000
Technical Assistance: 1-800-243-4630
e-a-r.com/hearingconservation.com
© 2010 3M Company.
3M and all other trademarks used herein
or hereon are trademarks of 3M Company,
used under license in Canada.
Author: Elliott H. Berger, M.S.,
3M Division Scientist
70-0715-7001-7
Printed in U.S.A.