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Management of Hearing Loss
Many causes of hearing loss have no cure. In these cases, treatment involves compensating for the hearing loss as much as possible. Most people with moderate to severe loss use hearing aids. People with severe to profound loss are greatly helped by a cochlear implant.
Sound amplification with a hearing aid helps people who have either conductive or sensorineural hearing loss. Unfortunately, a hearing aid does not restore hearing to normal. A hearing aid should, however, significantly improve a person's ability to communicate and enjoy sounds.
Many people are reluctant to wear hearing aids because of social stigma. Doctors should discuss such issues and encourage people to meet with an audiologist to evaluate the array of different hearing aid designs available. Some older people and those with arthritis or neurologic problems find it difficult to manipulate the smallest hearing aids and should consider slightly larger devices.
Hearing Aids: Amplifying the Sound
All hearing aids have a microphone to pick up sounds, a battery-powered amplifier to increase their volume, and a means of transmitting the sound to the person. Most hearing aids transmit the sounds through a small speaker placed in the ear canal. Other hearing aids, which require surgical implantation, transmit sounds directly to the bones of the middle ear (ossicles) or the skull instead of through a speaker. Hearing aids differ in how big the components are and where they are located. As a general rule, hearing aids with higher quality sound outputs may be more noticeable but are easier to adjust and offer listening advantages. Larger hearing aids can often accommodate features of assisted listening that are not available in small ones.
Hearing aids have different electronic characteristics that are chosen to suit the person's particular type of hearing loss. For example, people whose hearing loss affects mainly higher frequencies do not benefit from simple amplification, which merely makes the mumbled speech they hear sound louder. Hearing aids that selectively amplify the high frequencies markedly improve speech recognition. Other hearing aids contain vents in the ear mold, which facilitate the passage of high-frequency sound waves into the ear. Many hearing aids use digital sound processing with multiple frequency channels so that the amplification can even more precisely match the person's hearing loss. People who cannot tolerate loud sounds may need hearing aids with special electronic circuitry, which keeps the maximum volume of sound at a tolerable level.
Telephone use can be difficult for people with hearing aids. With typical hearing aids, placing the ear next to the phone handle causes squealing. Some hearing aids have a phone coil. With the flip of a switch the microphone is turned off, and the phone coil links electromagnetically to the magnet in the phone handle. As long as the hearing aid has the proper features, this setup can be arranged by the phone company with simple changes to the phone. Hearing aids with complex features tend to be the most expensive but are often essential to meet hearing needs.
Most profoundly deaf people who cannot hear sounds even with a hearing aid benefit from a cochlear implant. Cochlear implants provide electrical signals directly into the auditory nerve by means of multiple electrodes inserted into the cochlea, which is the inner ear structure containing the auditory nerve. A cochlear implant is needed when people with a hearing aid do not understand more than half the words in sentences. An external microphone and processor pick up sound signals and convert them to electrical impulses. The impulses are transmitted electromagnetically by an external coil through the skin to an internal coil, which connects to the electrodes. The electrodes stimulate the auditory nerve.
Cochlear Implant: A System for the Severely to Profoundly Deaf
A cochlear implant does not transmit sounds as well as a normal cochlea but does provide substantial benefit to the hearing impaired. It helps people read lips. Most people who have implants can distinguish words without reading lips and also use the telephone.
A cochlear implant also helps deaf people hear and distinguish environmental and warning signals, such as doorbells, telephones, and alarms. It helps them modulate their own voice to make their speech easier for others to understand. A cochlear implant is more effective in a person whose hearing loss is recent or who has successfully used a hearing aid before the implant.
People whose acoustic nerves have been destroyed, for example, by fractures of the base of the skull (temporal bone) that have occurred on both sides or by neurofibromatosis, cannot benefit from hearing aids or cochlear implants. However, they can have some hearing restored by having electrodes implanted in the part of their brain responsible for hearing (brain stem). The electrodes are connected to sound-detecting and sound-processing devices similar to those used for cochlear implants.
Several types of assistive devices are available for people who have significant hearing loss. Light alerting systems enable people to know when the doorbell is ringing or a baby is crying. Special sound systems help people hear in theaters, churches, or other places where there is competing noise. Many television programs carry closed captioning, with the dialog shown as visible text. Telephone communication devices are also available.
Lip reading (speech reading) is an important skill for people who have decreased hearing. It is particularly important for people who can hear but have trouble discriminating sounds, typically those with age-related hearing loss. Observing the position of a speaker's lips allows people to recognize which consonant is being spoken. Because people whose hearing loss affects high frequencies are unable to understand consonant sounds, lip reading can significantly improve the comprehension of speech.
Lip reading and other strategies for coping with hearing loss are sometimes taught by hearing professionals in a program called aural rehabilitation. In addition to training in lip reading, people are taught to gain control over their listening environment by learning to anticipate difficult communication situations and modifying or avoiding them. For example, people can visit a restaurant during off-peak hours, when it is quieter. They can ask for a booth, which blocks out some extraneous sounds. They can request that specials of the day be written rather than spoken. In direct conversations, people may ask the speaker to face them. At the beginning of a telephone conversation, people can identify themselves as being hearing-impaired.
People with profound hearing loss often communicate using sign language. American Sign Language (ASL) is the version most widely used in the United States. Other forms include Signed English, Signing Exact English, and Cued Speech.
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