How's your hearing?
The human ear is an engineering miracle. Sound waves strike a membrane called the eardrum, causing vibrations that the cochlea, a snail-like structure in the inner ear, converts into hydraulic pressure. Delicate hair cells transform the pressure into electrical impulses that shoot along the auditory nerve to the brain. The brain, in turn, informs us that we are hearing a wheat field rustle or a baby cry.
One of the most common--and most severe--types of hearing loss results from damage to the sensitive hair cells of the inner ear that receive sound waves, or from the malfunction of the sound-induced nerve impulses to the brain that are transmitted by the auditory nerve. Such sensorineural loss often grows progressively worse and is irreversible. There is no medical or surgical treatment for it. Some people are born with sensorineural hearing problems as a result of certain genetic diseases, exposure to German measles while in the womb, inadequate oxygen at birth or even a birth injury. The problem is also caused by aging, ear infections or even drugs that are toxic to the ear. However, the No. 1 cause of nerve deafness is prolonged exposure to loud noised, which can tear the eardrum blast away the hair cells inside. Because men are exposed to more industrial noise, they are slightly more prone to hearing disorders than are women. Airports, textile plants and construction demolition areas are the most common sites where job-induced hearing loss occurs. In our personal lives, much of the problem is due to excessively loud music or even to setting our televisions at too high a volume for too long a time. To make things worse, as our hearing ability decreases, we frequently turn the volume even higher.
Another type of hearing loss--conductive--may be congenital, brought on by malformations of the middle or outer ear. Conductive loss disrupts the transfer of sound waves from the external ear to the inner ear. Most conductive loss occurs in childhood, and can sometimes be treated by antibiotics or ear surgery. Causes range from excessive ear wax (which is treatable), middle-ear infection such as otitis media (a painful build-up of fluid in the middle ear) and premature birth to food allergy and otosclerosis (in adults), in which a bony growth blocks the small bone in the middle ear. Unlike sensorineural loss, conductive loss can be corrected through surgery, medical treatment or with a hearing aid.
Much congenital deafness is inherited from parents, but because of continuing improvements in antibiotics, corrective surgery and care for premature infants, fewer babies are likely to be deaf. "Advances in medical science have reduced significantly the incidence of some types of hearing impairment in childhood," says Hiroshi Shimizu, M.D., director of the Hearing and Speech Clinic Johns Hopkins University Medical School. On the other hand, Jerome Schein, Ph.D., director of the Deafness Research and training Center at New York University, says, "The deaf population is growing because the longer you live, the more probability there is of deafness from degenerative disease."
Medical advances are promising to make life radically better for the deaf in the years ahead. A new technique called auditory brainstem response (ABR) now enables audiologist (certified hearing specialists) to detect hearing difficulties in babies only ten months old. Most other hearing tests require subjects to signal when they hear a sound--a method obviously unsuitable for infants, who cannot follow such instructions. With this new approach, a lightweight headphone transmits tones to the infant while a computer hooked up to electrodes placed on her head records and analyzes the brain waves she emits.
Increasingly sensitive hearing aids are now so miniaturized that the microphone, amplifier, battery, receiver and controls can be housed in a one-ounce packet and be easily worn in or behind the ear or affixed to eyeglasses. An "all-in-the-ear-canal" hearing aid such as President Reagan's has increasing cosmetic appeal, because it fits nearly invisibly into the ear canal and weighs only a few grams. And a new, nonelectronic hearing aid, called an "Earesonator," is also in the works. "This may be the answer for mild hearing loss affecting more than a million Americans," says Richard L. Goode, M.D., professor of surgery at Stanford University School of Medicine.
Some people with conductive hearing loss can benefit from surgery. For those who might, one operation removes from the middle ear the defective stapes, or stirrup bone, crucial to hearing, and replaces it with an artificial device. And in a procedure called tympanoplasty, surgeons can reconstruct a shattered eardrum.
The most encouraging innovation in the treatment of congenital nerve deafness is the cochlear implant, an electronic device that restores some hearing to the totally deaf. "The patient hears sound that's like listening to a radio with static," says Janet Doak, vice president of planning and development at the House Ear Instsitute in Los Angeles, which has performed more than 300 implants on adults and 90 on children. "deaf people have a sense of sound, but they can't really make out speech itself-- the implant enhances their ability to lip-read."
How to detect hearing loss
The early stages of hearing loss may be hard to detect or easy to push aside. But you should see an audiologist or other medical ear specialist if you:
* routinely turn up the volume on the television or the stereo;
* miss dialogue in the movies unless you are near the loudspeaker;
* notice a ringing or buzzing in your ears;
* constantly ask people to repeat themselves;
* answer questions incorrectly because you misunderstand them;
* suffer frequent ear infections;
* are often told that you speak too loudly;
* can't distinguish between certain words, such as "cat," "sat," "fat";
* have trouble hearing on the telephone.
If you are taking any prescription drugs, such as streptomycin or neomycin, check to see if hearing loss can be a side effect. It's also a good idea to get your hearing checked with an audiometer at least once every two years, especially if you work in a noisy environment or regularly take any drugs that could damage your hearing.
If you use a radio-cassette player with earphones, keep the volume down. Continuous exposure to noise levels approaching one hundred decibels (a volume setting of four or above) can cause permanent hearing loss. And according to one hearing expert, listening at a volume setting of six or higher for only five minutes a day can result in hearing loss within a few years. In a disco or at a rock concert, if you have to shout to be heard or if the noise leaves a ringing in your ears, the sound level is high enough to inflict damage.
Rubella (German measles) can affect you unborn child's hearing. Ask your doctor if you should get a rubella vaccine. Some specialists warn that the vaccine, usually given to school-age children, may last only eight years in some cases. This can leave women of childbearing age susceptible to the disease, which impairs hearing in 60 percent of infants whose mothers have rubella during the first trimester of pregnancy.
To find a hearing specialist, check with your family doctor or county medical society. Or you can contact the National Association for Hearing and Speech Action, 10801 Rockville Pike, Rockville, Maryland 20852, or call toll-free (800) 638-8255 for a list of certified audiologists.
For futher information on hearing loss or deafness, contact the National Association of the Deaf, 814 Thayer Ave., Silver Spring, Maryland 20910 (distributes literature, videotapes); the National Center for Law and the Deaf, 800 Florida Ave. N.E., Washington, D.C. 20002 (publishes a newsletter); Gallaudet College (the liberal-arts college for the deaf), Kendall Green, Washington, D.C. 20002 (home of the National Information Center on Deafness); or call your state's society for the deaf.
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|Publication:||Saturday Evening Post|
|Date:||Oct 1, 1984|
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