If one has hearing issues to the point of consults a Los Angeles Audiologist, someone who studies the ear’s ability to pick up sounds and maintain equilibrium, one may be told that he or she can ameliorate hearing loss with a hearing aid. However, some individuals who require auditory assistance with such a device, may be curious as to how such a device actually functions. This article is written for the express purpose of explaining how a hearing aid aids the hearing capabilities of its user.
The earliest form of hearing aid, referred to as an ear cone or ear trumpet, was only useful in receiving audio out of a limited field, like a parabolic antenna. Sounds passing into the cone’s range would then funnel down and become amplified to a point where the user could hear it through the ear canal. However, as a passive device, listening cones had no real way to modify volume.
Body worn aids preceded the ear cone, consisting of a case (roughly the size of a deck of cards), carried around the waist or in one’s pocket, and an earmold connected to the case via a wire. An earmold is an impression of the user’s ear, made to optimize comfort and minimize audio feedback. This rigging involves a battery and an amplifier, housed within the case, which transmit sound to the listener’s ear as a loudspeaker.
Behind the Ear (BTE for short) models were the next step after “body aids,” but providing superior size and quality. BTE earmolds rest behind the pinna, or “exterior ear,” with the case resting across the front of the ear (and over the canal). Mini-BTE aids, or “on the ear” units, have cases which connect by either an earmold or a more comfortable ear piece. Lastly, “receiver in the canal” (CRT, RIC, and RITE are all common abbreviations) models have the loudspeaker positioned within the ear canal, held in place with inserts made of soft material.
Beyond BTE models, the “invisible in canal” (IIC) units fits completely within the ear canal, with some models using a cell phone to remotely modify input. Extended wear units are moisture-resistant and designed to be worn constantly for a short period of time, rather than being removed nightly or when bathing.
Bone anchored hearing aids (BAHA) are engineered to use bone conduction via a surgical implant within a patient’s skull. BAHA units are utilized in patients lacking an external ear canal, those with conductive hearing loss, as well as those with unilateral hearing loss.