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Your Health
Presented by University
Health Services Manoa
Noise-Induced Hearing Loss
Noise is detrimental to our physical and mental health, contributing to sleep
disorders, cardiovascular problems, anxiety and aggression. Perhaps the most
obvious noise-related health problem is hearing loss; without our knowledge,
environmental noise may permanently damage our hearing. A recent study conducted
by the National Center for Environmental Health estimates that 12.5 percent
of U.S. children ages 6 to 19 have noise-induced hearing loss in one or both
ears, and noise exposure may be responsible for damaged hearing in 10 million
Americans of all ages (one-fourth of all those suffering from hearing loss).
Noise exposure can cause both temporary and permanent hearing loss. "Temporary
threshold shift" is a dullness in hearing that we all may experience after
being in a very noisy environment; normal hearing returns over a short period
of time. "Permanent threshold shift" can occur after exposure to either
a very high level of sound or moderately high levels over a period of time.
Although this hearing loss is permanent, it is usually unnoticeable at first,
increasing over a number of years. The first sign of damage is often loss of
occasional words in conversation or difficulty hearing over the telephone. This
progresses to decreased ability to hear high frequency sounds like rustling
leaves, the notes of a flute, or consonants such as "s" and "ch."
Hearing aids do not restore noise-induced hearing loss, although they may help
somewhat. Damaging levels of noise also cause tinnitus, a ringing or roaring
in the head that sometimes is continuous, or pain in the ears.
How much noise is too much? Loud noise damages the microscopic hair cells that
convert sound waves in the ear into electrical signals sent to the auditory
nerve. The likelihood of enough damage to cause hearing loss depends on a combination
of personal sensitivity, sound pressure and length of exposure. Sound pressure
is measured in decibels (dB). Most people can hear sounds as soft as 0 dB, which
is about the sound level of faintly rustling leaves. A whisper is between 15–25
dB, and typical speech is around 55–65 dB. Sounds of about 85 dB (the level
of busy traffic or a bulldozer just idling) can damage hearing after about 8
hours of constant exposure. As sound pressure increases, damage is likely after
a shorter time period; a lawn mower (around 95 dB) may produce permanent damage
after only 1–4 hours. Earphones turned to a standard volume level 5 (about
100dB) can cause permanent damage if listened to for only 15 minutes a day.
A leaf blower or rock concert can reach 110–120 dB, and the same sound
pressure may result from listening to headsets that don’t seem to be that
loud; this level of sound becomes dangerous after only 30–120 seconds.
Fireworks, gunshots, ambulances and jet planes can all cause immediate, permanent
damage if one is very close to them.
What should one do to reduce the danger of hearing loss? Lower the volume on
TV or stereo, especially when using headphones, and be careful of turning up
the car stereo too high in order to hear over traffic and engine noise. At concerts
or other public events don’t stand close to loudspeakers; take frequent
breaks if possible, to rest your ears. Make earplugs a habit, at fireworks displays,
rock concerts, or sports events, or when using household or yard equipment.
Finally, we can all advocate for less noise and educate others about this health
risk.
For more information, consult the following government sites: the National
Center for Environmental Health and the Environmental
Protection Agency. Also, the following organizations are devoted to noise
education and advocating for noise reduction: Hear-it,
Dangerous Decibels
and the Noise Pollution Clearinghouse.
University
Health Services Manoa provides
clinical and educational services for faculty, staff and students of UH Manoa.
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