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An electronic amplifying device designed to bring sound into the ear; it consists of a microphone, amplifier, and receiver. SYN: hearing instrument.

- behind-the-ear h. h. that rests on the medial aspect of the pinna.

- completely in the canal h. (CIC) a h. that fits entirely in the external auditory canal and is not visible at the surface of the body.

- digital h. programmable h. that can be customized to the extent of the user's hearing loss.

- in-the-canal h. h. that is placed in the external auditory canal but is still visible.

- in-the-ear h. h. that fits into the shell of the ear.

hearing aid -.ād n an electronic device usu. worn by a person for amplifying sound before it reaches the receptor organs

a device to improve the hearing. Simple passive devices, such as ear trumpets, are now rarely used. An analogue hearing aid consists of a miniature microphone, an amplifier, and a tiny loudspeaker. The aid is powered by a battery and the whole unit is small enough to fit behind or within the ear inconspicuously. If necessary, aids can be built into the frames of spectacles. In a few cases of conductive hearing loss the loudspeaker is replaced by a vibrator that presses on the bone behind the ear and transmits the sound energy through the bones of the skull to the inner ear. Digital hearing aids are in some respects similar to analogue aids but in addition to the microphone, amplifier, and loudspeaker, they have digital-to-analogue converters and a tiny computer built into the casing of the aid. This enables the aid to be programmed to the patient's particular requirements and generally offers improved sound quality. See also bone-anchored hearing aid, cochlear implant, environmental hearing aid, implantable hearing aid.