Hearing loss is any reduction in a person's ability to detect sound.
Hearing is a complex process that consists of many steps. It begins when sound waves strike the outside of the ear. Sound waves are vibrations that occur in air. When sound waves hit the ear, they cause tissue in the ear to start vibrating.
The ear consists of three major sections: the external ear, the middle ear, and the inner ear. The external ear acts like a small sound-collecting tube. Sound waves enter the ear and pass down a narrow canal called the auditory canal. At the end of the canal, the sound waves strike a thin membrane called the tympanic (pronounced tim-PA-nik) membrane, or ear drum. They cause the tympanic membrane to begin vibrating.
Just beyond the tympanic membrane is the middle ear. The middle ear contains three bones called ossicles (pronounced AH-sih-kulls). Vibration of the tympanic membrane is passed along to the ossicles. They too begin to vibrate.
The ossicles are connected to the inner ear. The inner ear is filled with a clear, watery fluid. As the ossicles vibrate, they create another wave inside the watery fluid in the inner ear. This wave is similar to a water wave on a lake or the ocean.
In the last stage of hearing, the water wave in the inner ear collides with the auditory nerve. The auditory nerve picks up these vibrations and transmits them to the brain. The brain "reads" these vibrations as a sound.
Hearing loss can occur at any stage of this process. For example, sound waves may be blocked as they try to pass down the auditory canal. Or they may not be able to pass through the ossicles in the middle ear. Or they may not be transmitted through the liquid of the middle ear or along the auditory nerve. Finally, the brain may lose its ability to make sense out of the vibrations it receives from the auditory nerve.
Hearing loss is usually defined as being either conductive or sensory hearing loss. Conductive hearing loss is caused by damage to the external or middle ear. Sound vibrations are unable to pass down the auditory canal, across the tympanic membrane, and through the ossicles. Sensory hearing loss occurs in the inner ear and the auditory nerve. Sound waves may reach the inner ear, but they are not transmitted successfully to the brain.
Some possible causes and symptoms of hearing loss at each of the above stages are as follows:
Hearing loss can often be diagnosed with a physical examination. A doctor may look directly into a patient's ears to see if any blockage is present, such as an infection or tumor. Another test involves the use of a tuning fork. A tuning fork is a metallic instrument that vibrates when struck. The tuning fork is placed next to the ear or placed against the patient's head. The vibrations it produces result in a musical tone. The patient's responses can help the doctor determine the patient's range of hearing.
Another important tool in the diagnosis of hearing problems is the audiometer (pronounced aw-dee-AH-meh-tur). An audiometer is a device that produces very pure tones of differing pitch and volume (loudness). A patient is provided with earphones connected to the audiometer. He or she is then asked to indicate the level at which various sounds can be heard. The data provided by this test may diagnose the type and severity of a patient's hearing loss. Many other tests are available to diagnose hearing disorders within the inner ear, the auditory nerve, and the brain itself.
Conductive hearing loss can almost always be restored to some degree, if not completely. Some effective treatments include the following:
Sensory hearing loss presents more serious problems. It often cannot be cured. Fortunately, hearing aids can help restore some of the hearing loss. Hearing aids can be dispensed only with a physician's prescription. They can make hearing at least ten times better.
Hearing problems are common. A number of organizations have been formed to help people with hearing loss. Special language training is available for children with reduced hearing. They may learn both lip reading and sign language.
The prognosis for hearing loss varies widely. The likelihood of improvement depends on the type of hearing problem. Most conductive hearing losses can be cured. Normal hearing can be restored by relatively simple procedures. Sensory hearing loss is more difficult to treat. It can seldom be cured or repaired. Hearing aids can often provide people with near-normal hearing, however.
Many types of hearing loss can be prevented. Infections of the throat and upper respiratory (breathing) tract should be monitored carefully. These infections can spread to the ears. If the ears do become infected, they should be treated as quickly as possible.
Noise reduction can prevent a large number of hearing problems. People who work in noisy environments, for example, should always wear protective headgear. People who enjoy loud music should use some restraint in listening to their favorite performers. This step alone can prevent thousands of cases of hearing loss each year.
Carmen, Richard, ed. Consumer Handbook on Hearing Loss and Hearing Aids: A Bridge to Healing. Sedona, AZ: Auricle Ink Publishers, 1999.
Pope, Anne. Hear: Solutions, Skills and Sources For People With Hearing Loss. London, New York: DK Publishing, 1997.
Turkington, Carol A. The Hearing Loss Sourcebook: A Complete Guide to Coping With Hearing Loss and Where to Get Help. New York: Plume, 1997.
Wayner, Donna S. Hear What You've Been Missing: How to Cope With Hearing Loss: Questions, Answers, Options. New York: John Wiley & Sons, 1998.
Alexander Graham Bell Association for the Deaf. 3417 Volta Place, NW, Washington, DC 20007-2778. (202) 337–5220. http://www.agbell.org.
The League for the Hard of Hearing. 71 West 23rd St., New York, NY 10010-4162. (212) 741–7650. http://www.lhh.org.
Self Help for Hard of Hearing People, Inc. 79 Woodmon Ave., Suite 120C, Bethesda, MD 20814. (301) 675-2248. http://www.shhh.org.
Vessel, B., "Deaf Source." [Online] http://home.earthlink.net/~drblood (accessed April 26, 1998).