How hearing aids work
How they work
From microphone to ear canal
A hearing aid takes sound in, changes it, and puts it back out into your ear canal. What makes it a hearing aid rather than an amplifier is that the change applied is based on a measurement of your own hearing.
Inside the device
What happens to sound inside a hearing aid
Four stages, in order.
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The microphone picks up sound
One or more microphones convert sound in the room into an electrical signal. Where they sit on the device affects what they pick up from different directions.
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The processor changes it
The signal is adjusted according to settings applied for your ears — different pitches are handled differently, according to your audiogram.
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The receiver delivers it
A small speaker, called a receiver, puts the processed sound into your ear canal. In some styles it sits in the device; in others it sits in the canal itself.
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Your ear and brain do the rest
The sound still has to travel the normal route through your ear and be interpreted by your brain. This is why a device cannot simply restore what is not there, and why adjusting takes time.
Where it fits into the hearing pathway
A hearing aid delivers sound into the ear canal — which means everything from the eardrum inwards still has to do its job.
Sound enters the outer ear, vibrates the eardrum and three small bones, and is converted to nerve signals in the cochlea. Damage at different points causes different types of hearing loss.
Why it is a prescription, not a volume knob
Hearing loss is rarely even across pitches. It is very common to hear low pitches normally while high pitches need considerably more volume.
If a device simply made everything louder, the pitches you already hear well would become uncomfortable long before the pitches you struggle with became clear. So the processor applies different amounts at different pitches, based on your audiogram.
That is the reason a hearing test comes first, and the reason devices are adjusted rather than chosen by loudness.
Why it is checked while you wear it
Every ear canal is a different shape and size, so the same settings do not produce the same result in every ear. Because of that, settings are verified and adjusted with the device in your ear rather than assumed from the programming alone.
It is also why follow-up appointments exist. A first fitting is a starting point, not a finished job.
Common questions about how they work
Is a hearing aid just an amplifier?
No. An amplifier makes everything louder by the same amount. A hearing aid applies different amounts at different pitches, based on a measurement of your own hearing — which is why it has to be programmed to an audiogram.
Why do hearing aids need to be programmed?
Because hearing loss differs between people, between ears, and between pitches. The programming is what matches the device’s output to your own measured hearing rather than to an average.
Do hearing aids restore normal hearing?
No. A hearing aid changes the sound arriving at your ear; it does not repair the ear or the hearing nerve. Sound still has to travel through your ear and be interpreted by your brain. Anyone promising restored or normal hearing is overstating what a device does.
Why does my own voice sound different?
Putting something in the ear canal changes how you hear sound conducted through your own head — a common experience, often described as sounding boomy or blocked. It is one of the things adjusted during fitting and follow-up, so it is worth mentioning rather than putting up with.
What is the receiver?
Confusingly, in a hearing aid the receiver is the speaker — the part that delivers sound into the ear canal. In receiver-in-canal devices it sits in the canal itself rather than in the case behind the ear.
If you want your own hearing checked
Book a hearing appointment
This page is general information. A hearing test measures your own hearing and is the only way to know where yours sits.
Sources
- NZAS — Hearing aids
- NZAS — How does my hearing work?
- New Zealand Audiological Society — About hearing loss
- World Health Organization — Deafness and hearing loss — fact sheet
This page is general information, not a diagnosis or individual advice.
Hearing with Heart
Audiology & Ear Hygiene
Unit 34, The Acres,
Halswell, Christchurch 8025,
New Zealand