Hearing Aids Technology  

Intended Use  

A hearing aid is wearable sound-amplifying device that is intended to compensate for impaired hearing. Primarily useful in improving the hearing and speech comprehension of sensorineural hearing loss.

 

Description 

  • Hearing aids described in this section are 'Air Conduction' hearing aids (vs. a 'Bone Conduction' hearing aid that need a surgical implantation).

  • The hearing aid magnifies sound vibrations entering the ear. 

  • Surviving hair cells detect the larger vibrations and convert them into neural signals that are passed along to the brain. 

  • The greater the damage to a person’s hair cells, the more severe the hearing loss, and the greater the hearing aid amplification needed to make up the difference. 

  • However, there are practical limits to the amount of amplification a hearing aid can provide

  • In addition, if the inner ear is too damaged, even large vibrations will not be converted into neural signals; a hearing aid would be ineffective.

 

Hearing aids are made up of several components that work together to recognize, parse, and amplify sound:

  • Microphone picks up sound and converts it into electrical impulses

  • Amplifier circuitry with a computer chip called the digital signal processor (DSP) analyzes the incoming sound to amplify speech signals and limit unwanted noise

  • Receiver (miniature loudspeaker)  transforms the electrical impulses back into sound waves and redirects them into the ear canal

  • Batteries that power the electronic parts 

 

Analog hearing aids make continuous sound waves louder. These hearing aids essentially amplify all sounds (e.g., speech and noise) in the same way. Some analog hearing aids are programmable. These aids are less commonly available.

 

Digital hearing aids have all the features of analog programmable aids, but convert sound waves into digital signals and produce an exact duplication of sound. Computer chips in digital hearing aids analyze speech and other environmental sounds and allow for more complex processing of sound.  Have greater flexibility in hearing aid programming, provide multiple program memories and are the recommended type of hearing aids.

Other features include:

  • Directional microphone to help converse in noisy environments. Specifically, it allows sound coming from a specific direction to be amplified to a greater level compared to sound from other directions.

  • T-coil (Telephone switch) to switch from the normal microphone setting to a "T-coil" setting in order to hear better on the telephone. Works well in theaters, auditoriums, houses of worship, and other places that have an induction loop or FM installation. 

  • Direct audio input to plug in a remote microphone, FM assistive listening system, TV, connect to other devices such as computer, audio player etc.

  • Feedback suppression to suppress squeals when a hearing aid gets too close to the phone or has a loose-fitting earmold.

  • Wireless technology in its programming or use.

Styles

​Different styles of hearing aids use variations of same technology to create different fits in and around ear and to function slightly differently 

Behind-the-ear (BTE) aids: Most parts are contained in a small plastic case that rests behind the ear; the case is connected to an earmold or an earpiece by a piece of clear tubing. Easy to be cleaned and handled, and are relatively sturdy. 

"Mini" BTE (or "on-the-ear"), Receiver- in-ear (RIC) aids: Also fits behind/on the ear, but is smaller. A very thin, almost invisible tube is used to connect the aid to the ear canal. Allow not only reduced occlusion or "plugged up" sensations in the ear canal, but also increase comfort, reduce feedback and address cosmetic concerns.

In-the-ear (ITE) aids: All parts of the hearing aid are contained in a shell that fills in the outer part of the ear. Larger than the in-the-canal and completely-in-the-canal aids, and for some people may be easier to handle than smaller aids.

In-the-canal (ITC) aids and completely-in-the-canal (CIC) aids: Aids are contained in tiny cases that fit partly or completely into the ear canal. They are the smallest hearing aids available and offer cosmetic and some listening advantages. However, their small size may make them difficult to handle and adjust for some people.

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