hearing aid
an electronic device that amplifies sounds for people with hearing loss. The basic parts of a hearing aid include a microphone to collect sounds, a replenishable battery power supply, an amplifier to increase the volume of sounds, and a receiver to transmit the amplified sounds to the ear. Hearing aids are available in four different styles (behind the ear, in the ear, in the canal, and completely in the canal) and four different types: (a) conventional, which is the most basic and amplifies all sounds; (b) programmable, which adjusts the level of amplification of sounds according to a customized listening program; (c) digital, which automatically adjusts amplification and volume, is freer from distortion, and provides enhanced sound clarity and improved selective listening in noisy environments; and (d) disposable, which is comparable to a conventional hearing aid but must be replaced entirely once the battery wears out. See also assistive listening device;
cochlear implant.