![]() Another important feature in many modern instruments is the inclusion of a directional microphone that is able to partially suppress sounds from the back and sides of the wearer in some listening environments, on the assumption that sounds from these directions have less functional importance than sounds from in front. In addition, to accommodate the reduced range of sound levels available to typical hearing-impaired listeners, many instruments provide more gain for soft environmental sounds than they do for louder sounds: this is called wide dynamic range compression (WDRC) processing. It is typical to shape the frequency response to provide more amplification for frequencies for which the hearing loss is greater: this is called selective amplification. Most hearing aids also modify sounds somewhat to attempt to compensate for specific features of the individual hearing loss. Conventional bone conduction devices use a BTE-style case and incorporate a vibrator that is held against the skull using a spring headband.Īt the most basic level, a hearing aid simply increases the loudness of sounds presented to the impaired ear. In-the-canal (ITC) models are smaller ITE versions that fit mostly into the outer end of the ear canal.Ĭompletely-in-the-canal (CIC) models are the smallest devices and fit entirely inside the ear canal.īone conduction hearing aids are used only when the ear canal is not able to accommodate or tolerate the insertion of an air conduction device. This type of hearing aid fits into the concha of the ear. ![]() In-the-ear (ITE) models are manufactured with all the components inside the custom earmold. Current air conduction hearing aids are almost all worn at ear level, and there are several different styles.īehind-the-ear (BTE) models fit snugly over the pinna of the external ear and deliver sound to the ear canal through a plastic tube and plug (earmold). Finally, all hearing aids require a power source (battery).Įarly hearing aids were worn on the body or carried in a pocket, but these types are very seldom seen today. Bone conduction instruments deliver energy to the cochlea by vibrating the skull with a small transducer. In addition, air conduction instruments include a miniature loudspeaker (called a receiver) to generate the amplified sound, which is routed into the ear canal. They include a microphone to pick up sound energy, an amplifier to boost the level of the signal, and various filters and other devices that modify the sound to match it more precisely to the needs of the impaired listener. The chapter briefly describes the main types of devices and discusses some of the issues involved in their provision and use.Ĭonventional wearable hearing aids are self-contained amplifying systems. In addition, there is a class of ancillary devices called assistive listening devices (ALDs) that may be used alone or in combination with hearing aids or implants. Wearable personal devices include hearing aids and cochlear implants, as well as auditory brainstem implants. This chapter reviews the variety of devices that typically are used to ameliorate the effects of hearing loss. Many individuals find that the positive benefits of the prosthesis do not outweigh the negative consequences (such as ear discomfort, feedback squeal, high cost, and stigma), and they may elect to continue without correction. Prosthetic correction for hearing impairment is often not as successful as vision correction, leaving the individual with substantial residual limitations. The process of achieving the best hearing correction for an individual can be long and complicated. Hearing aids cannot be fitted like eyeglasses, whereby a quick refraction arrives at a prescription that provides the “best correction” almost immediately. In disability determination for people with hearing loss, how should the Social Security Administration (SSA) account for the potential benefits that the individual might receive from a sensory aid? In determining vision-based disability, SSA mandates testing with “best correction,” but for claimants with hearing loss, currently most SSA guidance directs that they should be tested without correction. ![]()
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