A hearing aid amplifies and processes sound in much the same way that a stereo sound system does. However it is much more complex, because all of the technology has to fit into a tiny device that can sit in, or on, the ear.  A hearing aid consists of three major components, all protected by a plastic case which can be fitted on or in the ear.

The first component is a microphone, which changes sound in the air into an electrical signal.

The second component is an amplifier. The amplifier increases the intensity of the electrical signal. Amplifiers also use filters, which have the ability to selectively modify sound, so only the sound needed by the person with the hearing loss is amplified. Some filters can filter out unwanted noise.

The third component is a speaker. The speaker changes the electrical signal which has been amplified and filtered back into an acoustic signal which the wearer hears. The person wearing the aid can adjust the volume for clarity of the sound.


The cost of a hearing aid is relatively high, due to the fact that the components have to be miniaturised. Imagine the complexity of having to make speakers and microphones which are small enough to fit into a custom made case which is small enough to fit on or in the ear.

Hearing aids require special batteries, which are extremely small. These batteries may last from a few days to a few weeks, depending on the type of hearing aid and the amount of time used.

Hearing aids need very little special care. They are built to be durable, but like any other electronic device, they can be broken when dropped. Water can also cause damage. Ear wax can plug the opening for sound in the ear mold. Wax should be washed from the ear regularly. Ear wax guards, which can be put on the hearing aid, is also available.


2002 - 2009 The Society of Hearing Aid Acousticians
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