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February 14, 2003

HealthBeat: Choosing Hearing Aids

From: WHOI, IL - 14 Feb 2003

Rebecca Somach

The Ear and Hearing

There are three main parts to the ear: the outer, middle, and inner ear. Sounds waves are captured in the outer, visible portion of the ear and travel down the ear canal, where they bounce against the eardrum (a thin membrane that separates the outer ear from the middle ear). The sound vibrations bounce off the eardrum and are transmitted to three tiny bones – the hammer, anvil, and stirrup. The bones transmit the vibrations to the cochlea in the inner ear. This snail-shaped structure contains tiny hair cells that detect distinct tones and convert sound vibrations into nerve impulses. The impulses travel through the acoustic nerve to the brain, where they are recognized as sounds.

Hearing Loss

There are two main types of hearing loss: conductive and sensorineural. Conductive hearing loss occurs when sound is unable to clearly reach the inner ear. In some cases, obstruction in the ear canal, such as ear wax build-up or a foreign body, can impede sound. Some other causes include malformation of one or more of the hearing structures or fluid in the ear (from a cold, allergy or ear infection).

Sensorineural hearing loss occurs when the hearing structures in the cochlea or the nerve pathways to the brain are damaged or absent. One important cause of sensorineural hearing loss is chronic exposure to excessive noise, which damages the hair cells in the cochlea. The condition can also be caused by aging, infection, trauma, use of certain drugs, or tumor. In addition to a reduction in the volume of sound, patients have difficulty hearing clearly.

According to the American Speech-Language-Hearing Association about 28 million Americans have some degree of hearing loss. The problem affects 14 percent of people 45 to 64 and more than half of those 65 and older. Hearing loss can lead to difficulties in school, work, or social relationships. In some cases, patients may be unable to hear a ringing telephone, doorbell, or alarm.

Choosing a Hearing Aid

People with hearing loss need to be evaluated by a physician to determine the cause of the problem. Sometimes treatment of an underlying problem can restore hearing (for example, removal of excess ear wax). Patients also need to be evaluated to make sure there are no hidden medical problems causing the hearing loss. Once a patient has a medical evaluation, an audiologist can perform a hearing test. Through a thorough hearing evaluation, the hearing specialist can determine the nature of the problem and recommend ways to improve hearing.

Many people with hearing loss can be helped with hearing aids. There are four main styles of hearing aids. Behind-the-ear devices are worn behind the ear and held in place by a custom ear mold and clear tubing. In-the-ear devices are custom-made to fit entirely in the ear, visibly covering the ear canal and a small portion of the outer ear. In-the-canal hearing aids are designed to fit inside the ear canal. They are less visible than in-the-ear devices, but can still be seen. Completely-in-the-canal hearing aids are the smallest and least visible devices. They are designed to fit deeper into the ear canal. In general, the smaller hearing aids are best for people with minor hearing loss. Those with significant hearing loss often require larger devices that contain bigger components and batteries that are more powerful.

Conventional hearing aids are analog devices that simply amplify sound. They are the least expensive types of hearing aid, but they have an important limitation. Analog hearing aids amplify all sounds. So in some situations a user may have difficulty distinguishing between conversations and background noise. Digital hearing aids have multiple channels that control pitch and volume. These devices can be individually programmed to adjust for various listening situations and provide the best “hearing” for a wearer.

With so many different sizes, styles, and features of hearing aids available, patients should seek advice from a certified hearing specialist for help in selecting the most appropriate type. It takes time for a wearer to adjust to a hearing aid. So ask about a trial period. Hearing aid dispensers should give clients at least 30 days to return or exchange a device. Many hearing specialists recommend getting two hearing aids – one for each ear. Quality hearing in both ears is important to pick up the direction of sounds, discriminate between voices, and clearly understand conversation.

With a proper fit and adjustment, most hearing aid wearers will be very happy with their purchase. However, patients still need to have realistic expectations. Hearing aids can improve hearing, but are not a cure for hearing loss and won’t necessarily produce the same quality of sound as the natural ear.

Audience Inquiry

For information about hearing loss or hearing aids:
American Academy of Audiology, 11730 Plaza America Dr., Suite 300, Reston, VA 20190,
Alexandria: American Academy of Otolaryngology,
American Speech-Language-Hearing Association,
Federal Trade Commission,
House Ear Institute,
National Institute on Deafness and Other Communication Disorders, National Institute of Health, 31 Center Dr., MSC 2320, Bethesda, MD 20892,

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