When you notice a difference between loud sounds and quiet ones, your
ears are perceiving changes in sound pressure level. Intensity (or volume)
is measured in decibels (dB). Zero (0) dB is the softest sound that can
be heard. Normal conversation is around 40dB to 60dB, a whisper around
30dB. A rock concert can average between 110 and 120 dB. Pain from hearing
is subjective. Levels below 125 dB may be painful to some individuals.
The sound from a jet plane is approximately 140 dB.
At rock shows, the dB level can be as great as 140 dB in front of the
speakers, but less than 120 dB at the back which is still very loud and
are measured on a logarithmic scale. Each increase of 10 on the scale
represents a tenfold increase in loudness. 20 dB is 10 times as loud as
10 dB; 30 dB is 100 times louder than 10 dB, and so on.
The maximum exposure time for unprotected ears per day is 8 hours at
90 dB SPL, A-weighted, slow response according to The Occupational Safety and Health Administration (OSHA)
guidelines. For every 3 dB increase in volume, the maximum exposure time
is cut in half.
95 dB - 4 hours
100 dB - 2 hours
110 dB - 30 min
120 dB- 7.5 min
Many hearing professionals believe that these permissible levels are
still too high for hearing safety. NIOSH, the National Institute for Occupational Safety and Health recommends 85 dB for eight hours a day.
Other sources of noise: boom cars, bars, dance clubs, motorcycles, auto
races, monster trucks, farm and factory equipment, power tools, guns,
sporting events, crowd noise, stereo headsets.
Noise-induced hearing loss affects both the quantity and the quality
of sound. Understanding human speech becomes difficult because words become
indistinct. Excessive sound exposure damages hearing by over-stimulating
the tiny hair cells within the inner ear. There are between 15,000 and
20,000 of these microscopic sensory receptors in the cochlea (coke-lee-ah).
When these hair cells are damaged, they no longer transmit sound to the
brain. Sounds are muffled. Hearing damage through noise exposure is permanently
lost. Hearing aids amplify the remainder of your hearing.
Is Your Hearing at Risk?
After exposure to loud music or noise you may experience one or more of
Ringing or buzzing in the ears
Slight muffling of sounds
Difficulty in understanding speech. You can hear all the words, but
you can't understand them.
Difficulty in hearing conversation in groups of people when there
is background noise, or in rooms with poor acoustics.
If you experience any of these early warnings, don't wait
to seek help. Have your hearing checked by an audiologist,
or have your ears examined by an ear specialist. Protect your
hearing by wearing ear plugs or turning down the volume. Take
breaks. Give your ears a chance to recover.
Who is an Audiologist
Who is an Otolaryngoloist
Types of Hearing Aids
How Our Hearing Works
The OUTER EAR acts like a funnel to direct sound
waves from the air to the tympanic membrane (eardrum). Sound causes the
tympanic membrane to vibrate. These vibrations cause the three bones in
the MIDDLE EAR (malleus, incus, and stapes) to move mechanically. The
middle ear sends these mechanical vibrations to the INNER EAR, where they
are picked up by tiny hair cells (cilia) and sent as electrical impulses
along the auditory nerve to the brain.
Hearing Loss: It's A Matter of Degrees
Degree of Hearing Loss can be mild, moderate, severe, or profound.
Mild (25-40 dB). A person with a mild hearing loss will have difficulty
following conversation if the speaker is more than six feet away or if
there's noise in the background.
Moderate (40-70 dB). A person with moderate hearing loss would be able
to hear if the speaker is speaking loudly and at no more that 3 to 5 feet
away. They'll also have trouble hearing with background noise and will
need to wear a hearing aid to hear conversation.
Severe (70-90 dB). A person with a severe hearing loss would be able
to hear someone's voice if the speaker shouts and is 1 foot away. Without
a hearing aid the person would not be able to understand speech and only
be able to hear some loud sounds( a siren, for example).
Profound (91 dB or more). A person with a profound hearing loss is only
able to hear very loud sounds. With hearing aids they would probably be
able to hear loud sounds, like perhaps a telephone ringing or a name being
called but, it would be difficult to understand speech. With training
their ability for understanding some speech may improve.
Types of Hearing Loss
28 Million Americans have a hearing loss; 80% of those affected have
hearing damage that is irreversible and permanent.
17 million Americans are affected by sensorineural hearing damage resulting
from heredity, birth, trauma, disease, advanced age, or exposure to noise.
A sensorineural hearing loss is damage to the hearing nerve in the inner
Advances in hearing aid technology have made great improvements
in total or at least partial rehabilitation. They can assist in understanding
speech and improving the clarity of sound. They cannot restore hearing
to normal in the way that eye glasses correct vision.
When there is difficulty in both the middle and inner ear, a mixed hearing
loss (conductive and sensorineural) exists.
A conductive hearing loss occurs when the hearing nerve functions properly
but there is difficulty in the outer or middle ear transmitting system.
Sound can not conduct properly to the inner ear nerve or cochlea.
Conductive hearing loss can be the result of many different conditions.
The most common is fluid in the middle ear. Fluid builds up behind the
ear drum which sometimes becomes infected. This can be treated with antibiotics
and other medications. If drug therapy fails, drainage can be accomplished
through a small incision in the eardrum (myringotomy). Tubes may be inserted
to provide middle ear aeration.
Otitis media is the most common form of temporary hearing loss among
Another cause of conductive hearing loss is the fixation of the hearing
bones (otosclerosis) which can be corrected through a surgical procedure
called a "stapedectomy." Holes or perforations in the eardrums
and damaged hearing bones can be corrected by reconstructive surgery.
Hearing loss may be a symptom of ear disease. It is important to have
your hearing examined by an ear specialist, (otologists or an otolaryngologist),
or have your ears evaluated by an audiologist.
Rehabilitation advances in speech reading, counseling, auditory training,
hearing aids and assistive listening devices (ALDs) help overcome the
handicap of hearing loss. Hearing aids are now available that fit entirely
within the ear canal and are practically invisible to the human eye.
Hearing loss in the profoundly deaf can sometimes be aided by a cochelear
implant. This is a device which consists of a magnetic coil placed in
the mastoid bone behind the ear. An electrode connects to the inside of
the inner ear and stimulates the hearing nerve which enables sound to
2 Million Americans are Profoundly Deaf
There is a difference between being deaf and being hard-of-hearing. People
are either born deaf or become deaf later in life through accident or
illness. American Sign Language (ASL) is used by most culturally deaf
people as their primary means of communication. ASL is recognized as a
language of its own and is the fourth most commonly used language in the
United States. Hard-of hearing people usually use their residual hearing
and communicate verbally.