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How A Hearing Aid Works

How does a hearing aid work? Hearing aids come in many shapes, sizes and colours. They all have very similar technology, although some are more advanced than others. Learn more about the components and what they do...

How do hearing aids work?

HD 91 Hearing AidHD 91
At its most simplistic there are four major electrical components of a modern hearing aid, all packed into a tiny cover. They are:

1) The Microphone

This may be a single microphone with a single port which would not enable the hearing aid to have a directional function. It can also be a single microphone with two ports which does provide some limited directionality function. The aid could have dual microphones which, when aligned to a sophisticated chip, can provide a variety of directional functions. The microphone gathers the sound from the environment, changes it from an analogue sound wave to a digital electronic signal and passes the signal on to the microchip or processor.

2) The Microchip

This is the core of the hearing aid. It takes the incoming sound from the microphone and processes it according to the programmed algorithms. The incoming signal may be divided into a number of frequency bands so that the chip can apply differing degrees of amplification to different frequencies. This allows the chip to shape the frequencies transmitted to the ear. With the vast majority of hearing losses there is a need to apply greater amplification to the higher frequencies. Modern day microchips or DSPs (digital signal processors) work very much faster than their predecessors, have a much greater capacity for multiple functionality and are very much smaller, so capable of providing sophisticated technology in the smallest of devices. Some hearing aids also have directional technology in the chip, which helps to distinguish between speech and background noise by using a trademarked tracking technology.

3) The Receiver

Ironically the Receiver does not receive sound, that’s the role of the microphone, it transmits sounds. The Receiver is a miniature loud speaker and connects to the microchip. It turns the electronic signal into a sound wave and passes this directly into the ear. Usually it is protected from damage through wax or moisture. In the case of RIC (Receiver in Ear) hearing aids the Receiver is positioned at the end of a tube inside the ear canal and connected by a wire to the main part of the hearing aid.

4) The Battery

A hearing aid is an electrical device and therefore requires a source of electrical power. Hearing aid batteries come in a variety of sizes. There are also a variety of different types, including rechargeable, but by far the most common is Zinc Air. All of these components fit inside a casing that goes either in the ear or behind the ear. Sound is delivered either electronically having been converted into an electrical signal or as an actual sound wave down very thin tubes. These tubes can be fed directly into the ear canal or be secured within an ear mould which is usually custom made to fit an individual’s ear. At its simplest a hearing aid takes sound in through the microphone, amplifies it with a microchip processor and transmits it into the ear from the receiver

Other components

Image of tubes and domes for hearing aids Spare tubes and domes

The Tube

A tube is used in BTE (Behind the Ear) and RIC hearing aids. It connects the components in the case behind the ear to the dome in the ear canal. In the case of a BTE aid the sound travels down the tube into the ear and in the case of a RIC aid the tube contains a small wire connecting to the Receiver (a speaker) covered by a dome

The Dome

A dome is usually a soft silicone dome that fits securely onto the end of the tube or the end of the hearing aid in the case of ITE (In the Ear) or CIC (Completely in Canal) hearing aids, making a comfortable fit in the ear canal. There are several types, the most significant difference being between open and closed domes. Open domes have holes allowing sound from outside to enter the ear which may help if you also suffer from tinnitus.

About Hearing Direct

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Author: Gary Hill

Gary our Hearing Aid Expert
Gary comes from 16 years’ experience in the hearing aid industry in both manufacturing and retail. Before co-founding HearingDirect, Gary was Marketing Director for a leading global hearing aid brand; GN ReSound where he worked for the UK sales division and latterly in their global headquarters in Copenhagen. He was responsible for developing and launching major global hearing aid models, conducting extensive research into the needs of the hearing impaired community and their performance demands of hearing aids and other devices.
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