Download What is Hearing Loss

What is Hearing Loss?
Understanding How the Ear Works
Sound waves carried through the air are captured by the outer ear. From there they
are converted first to vibrations in the middle ear and to electrical impulses in the
inner ear. The tiny hair cells of the cochlea transmit these impulses along the auditory
nerve to the brain, where they are translated into sound information. Hearing loss
occurs when hair cells lining the cochlea are damaged by sudden blasts of noise or
continued unprotected exposure to loud noise. For example, close proximity to an
explosion, industrial workplace noise, or having the volume turned up too high for too
long may cause damage to the hair cells in the cochlea, which is cumulative,
permanent and irreversible. Other causes include disease, repeated ear infections,
wax build-up, or abnormalities of the tiny bones of the ear.
Causes of Hearing Loss
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33.7% -- Overexposure to noise
28% --Aging - we begin to lose our hearing in our 30's and 40's by 65 years, more than half of us will
have a hearing loss. Most people will still be in their working years when they realize they have a hearing
loss
17.1% --infection or injury
4.4% -- genetics
16.8% -- other
National Centre for Health Statistics, USA
Signs of Hearing Loss
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You miss parts of conversations and continually ask people to repeat themselves
The high and low tones disappear - you don't hear birds singing anymore
Your family complains you have the TV up too loud
You have to turn up the volume on the telephone to hear properly
You can't distinguish speech from background noises - you can't follow dinnertime conversation with
others are talking and music playing
You find yourself straining to read lips and facial expressions to understand what someone is saying to
you
Noise Level: What’s Safe?
For the protection of public health, the Environmental Protection Agency proposed these
levels:
Neighborhoods - During waking hours 55 dB
Neighborhoods - During sleeping hours 45 dB
Classrooms - during teaching sessions 35 dB
Hospitals - during waking hours 45 dB
Hospitals - during sleeping hours 35 dB
For the workplace, the Occupational Safety and Health Administration (OSHA) proposed
these permissible noise exposure times (I have included examples of sounds at various
levels for easier understanding):
85 dB and higher - prolonged exposure will result in hearing loss
90 dBA - no more than 8 hours per day (examples - lawn mower, truck traffic, hair dryer)
95 dBA - no more than 4 hours per day
100 dBA - no more than 2 hours per day (example - chain saw)
105 dBA - no more than 1 hour per day
110 dBA - no more than ½ hour per day
115 dBA - no more than ¼ hour per day (preferably less)
140 dBA - NO EXPOSURE TO IMPACT OR IMPULSE NOISE ABOVE THIS LEVEL
(examples - gunshot blast, jet plane at takeoff)
The Academy of Pediatrics and the National Campaign for Hearing Health states 85 dB
is the threshold for dangerous levels of noise.
The National Campaign for Hearing Health's Toxic Noise Guidelines (exposure times
and decibel levels that cause hearing loss)
85 dB 8-hour period
85 - 90 dB 2-hour period
90 - 100 dB 1 to 2-hour period
100 - 110 between 2 and 15 minutes
110 - 120 less than 30 seconds
130 dB ANY EXPOSURE WILL RESULT IN PERMANENT HEARING LOSS
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If you frequent rock concerts, you are routinely exposed to sound levels
above 100 decibels. The closer you are to the speakers, the greater the risks
involved.
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Audiologists who studied sound levels in 22 Halifax bars over a four-year
period reported that all but one of them consistently registered noise levels
above 85 decibels; the average noise level was just under 100 decibels.
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Portable cassette players are capable of producing sound levels of more than
115 decibels at the ear. While some studies have found unalarming listening
levels among users of these devices, a Michigan audiologist’s research has
shown that almost everyone who participated in his study, including his fellow
audiologists, listened above a safe level.
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Some car stereos are capable of volume output as high as 140 to 150
decibels.
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Noise levels in a Toronto clothing store were measured at an intrusive 81
decibels, the same level as noisy traffic.
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Peak sound levels from gunfire may reach 170 decibels.
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A study of noise levels from firecrackers found that the average sound level at
a distance of 3 meters was 150 decibels; another study found that the
average sound level at this distance was 125 to 156 decibels.
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Studies of early-model cordless telephones have shown that the sound
pressure level of the ring signal may reach 140 decibels.
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A study of noise levels received by players of electronic arcade games found
normal settings ranging from 73 to 111 decibels.
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Montreal researchers measured the following sound levels from seemingly
harmless children’s toys: a toy xylophone, 129 decibels; a toy drum, 122 decibels;
a rattle, 110 decibels; a toy trumpet, 95 decibels; a cap gun, 138 decibels.