Hearing aids
Hearing Aid
A hearing aid is an electroacoustic body worn apparatus which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as an "ear trumpet" or "ear horn", were passive funnel-like amplification cones designed to gather sound energy and direct it into the ear canal. Similar devices include the bone anchored hearing aid, and cochlear implant. Body worn aids This was the first type of hearing aid invented by Harvey Fletcher while working at Bell Laboratories. Thanks to developments in technology they are now rarely used. These aids consist of a case, an ear mold, and a cord. The case contains the amplifier components. The case is about the size of a pack of playing cards and is worn in the pocket or on a belt. The ear mold is connected to the case via a cord. Because of their large size, body worn aids can provide loud amplification. This made them appropriate for profound hearing losses. Today, body aids have largely been replaced by Behind-The-Ear (BTE) instruments. Behind the ear aids (BTE) BTE aids consist of a case, a tube and an earmold. The case is small and made of plastic. It fits behind the pinna (ear). The case contains the amplification system. The tube is used to route the sound from the hearing aid case to the earmold. Typically the sound is routed acoustically. Sometimes the sound is routed electrically. In that case, the speaker is located in the earmold instead of in the case. The earmold is usually custom made or made of other pliable fixture that contours to the individuals ear. The color of the BTE components (case, tube and earmold) range from inconspicuous skin tones to bright colors and optional decorations.
Hearing Impairment
Hearing impairment or Deafness refers to conditions in which individuals are fully or partially unable to detect or perceive at least some frequencies of sound which can typically be heard by members of their species. Use of the term impaired implies that deafness presents an inherent disadvantage to an animal, a view that is rejected within the Deaf culture movement, where the terms Deaf and hard of hearing are preferred.
Hearing sensitivity is indicated by the quietest sound that an individual can detect, called the hearing threshold. In the case of people and some animals, this threshold can be accurately measured by a behavioral audiogram. A record is made of the quietest sound that consistently prompts a response from the listener. The test is carried out for sounds of different frequencies. There are also electro-physiological tests that can be performed without requiring a behavioral response.
Normal hearing thresholds are not the same for all frequencies in any species of animal. If different frequencies of sound are played at the same amplitude, some will be perceived as loud, and others quiet or even completely inaudible. Generally, if the gain or amplitude is increased, a sound is more likely to be perceived. Ordinarily, when animals use sound to communicate, hearing in that type of animal is most sensitive for the frequencies produced by calls, or, in the case of humans, speech. This tuning of hearing exists at many levels of the auditory system, all the way from the physical characteristics of the ear to the nerves and tracts that convey the nerve impulses of the auditory portion of the brain.
Approaches to Treatment
If the hearing loss occurs at a young age, interference with the acquisition of spoken language and social skills may occur. Hearing aids, which amplify the incoming sound, may alleviate some of the problems caused by hearing impairment, but are often insufficient. Cochlear implants artificially stimulate the VIIIth Nerve by providing an electric impulse substitution for the firing of hair cells. Cochlear implants are not only expensive, but require sophisticated programming in conjunction with patient training for effectiveness. People who have hearing impairments, especially those who develop a hearing problem in childhood or old age, require support and technical adaptations as part of the rehabilitation process. Recent research shows variations in efficacy but some studies show that if implanted at a very young age, some profoundly impaired children can acquire effective hearing and speech, particularly if supported by appropriate rehabilitation such as auditory-verbal therapy.