A hearing aid microphone is a device that receives sound that is amplified by a hearing aid and directed into the ear canal of a person who has suffered a loss of hearing. Depending on the style of the hearing aid, the hearing aid microphone might be located in the ear, around the ear or on the body. Hearing aid microphones are either directional, omnidirectional or directionally adaptive. A hearing aid user might choose to use different types of hearing aid microphones for different listening environments.
Modern hearing aids typically are designed as a single unit small enough to fit in or around the ear. Such devices feature a microphone located within or near the ear, affording the user natural hearing abilities with respect to which sounds will be perceived. These types of hearing aid microphones also provide the user with the best possible ability to discern where a sound is coming from. Feedback can be an issue, however, because the microphone is located near the speaker that outputs the amplified sound to the ear of the user.
Some hearing aid users prefer to wear the hearing aid microphone on the body. One common type of on-the-body microphone is designed to look like a necklace, receiving sound at the chest of the user. This type of hearing aid microphone can be particularly useful for individuals who have suffered severe hearing loss and who want to avoid feedback. Older on-the-body hearing aid microphones require a wire that leads from the microphone to the hearing aid itself. Newer devices use wireless technology to transmit sound from the microphone to the hearing aid, and no wires are required.
All hearing aid microphones are designed as either omnidirectional, directional or directionally adaptive. An omnidirectional microphone receives sound from all directions. This can lead to background noise interference in some cases. A directional microphone receives sound from only one or more directions and is generally desirable except in cases where the user needs to be able to perceive background noises. An adaptive microphone automatically switches between omnidirectional and directional depending on the listening environment.
Although technically not a hearing aid microphone, a telecoil is a similar device. It is a special circuit inside a hearing aid that picks up magnetic signals and converts them into sound for the hearing aid user. Telephones and some assistive listening devices produce electromagnetic signals. When a hearing aid is switched into telecoil mode, the hearing aid microphone is switched off, allowing the user to hear only the electromagnetic signals generated from the telephone or assistive listening device without any interference from background noise.