Your turn
Each lab is one step from the video. Tap, slide and switch, and see what happens.
Each lab isolates one part of the story. The hearing patterns are made-up examples, not real hearing-test data and not a hearing test.
Tap the buttons and slide the sliders.
Turn the hearing aid off and on. Which notes stop reaching grandpa?
With a typical high-frequency loss, the high bands drop out first. Switch the aid and compare.
Turn the hearing aid off and on. Where do the high notes go?
The bars are a made-up example, not a real hearing test.
Slide the pitch. Which hair cells wobble? Then show damaged cells.
High frequencies peak near the base, low ones toward the apex. Damaged base cells take the high pitches with them.
Slide from low to high. Watch the tiny hairs wiggle!
Tap each part to follow the sound from microphone to receiver.
Microphone → digital processor → amplifier → receiver, all powered by a battery.
Tap each part of the hearing aid.
Pick a hearing pattern, then drag the sliders until every band gets through, but not too loud.
Set the gain in each band to fill the gaps without pushing well-heard bands past comfort. Compare with "turn everything up".
Pick a pattern, then slide the sliders. Can you make every sound just right?
Made-up example patterns, not real hearing-test numbers.
Switch the features on and off. When does the voice stand out most?
Two microphones favour the front; noise reduction lowers the steady hum; turn feedback control off to hear why it matters.
A simplified picture of what the features do.
Compare the hearing aid path with the cochlear implant path, then set a headphone volume.
An aid amplifies for the remaining hair cells; an implant bypasses them. Then try the WHO's 60% guideline.
Slide the headphone volume. Keep it in the green!
A hearing aid is a tiny sound helper. People wear it in or behind the ear, to help them hear.
Sound goes into your ear and makes a thin skin shake, like a drum. Tiny bones pass the shake into a little snail shape full of water. Inside are tiny hair cells. When they wiggle, they send a message to your brain.
Very loud noise, and getting older, can hurt hair cells. Hurt hair cells don't grow back. Often the ones for high sounds, like birdsong, get tired first.
A tiny microphone catches the sound. A tiny computer works out which sounds need help, and makes them bigger. A tiny speaker plays them into the ear. A battery makes it all go.
A hearing check shows which sounds are hard to hear. The hearing aid helps those sounds the most. Quiet sounds get lots of help and loud sounds get only a little, so loud sounds aren't made much louder. Very loud noise can still hurt your ears.
This page explains how the body works; it isn't medical advice. If you're worried about your hearing, talk to a doctor or an audiologist.
A hearing aid is a tiny, computer-powered sound system that you wear in or behind your ear. A microphone picks up sound and turns it into an electrical signal. A chip turns that signal into numbers, splits it into bands from low to high pitch, and boosts the bands the wearer hears less well, often the high ones. An amplifier adds power, and a tiny speaker called the receiver plays the adjusted sound into the ear canal. A battery powers it all.17
Hearing aids don't give back "normal" hearing. They make sound bigger so the ear's remaining hair cells can pick it up.18
To see what a hearing aid helps, follow a sound into the ear:2
The hair cells are arranged a bit like the keys of a piano. Cells near the wide end of the cochlea respond to high pitches, like a baby crying; cells near the centre respond to low pitches, like a big dog barking.2 People can hear from about 20 to 20,000 vibrations per second (hertz).18
Hair cells can be damaged by loud noise, by aging, and by some illnesses and medicines. In people, damaged hair cells don't grow back.413 Often the high-pitch end is hit first: noise damage tends to start with sounds like bells or birdsong, and age-related loss makes high voices and sounds like "s" and "th" harder to catch.1113 This kind of hearing loss, from the inner ear, is called sensorineural hearing loss, and it's the kind hearing aids mostly help.1
Most hearing aids share the same basic parts, whatever their shape:71
| Part | What it does |
|---|---|
| Microphone | Picks up sound and turns the sound waves into an electrical signal1 |
| Chip (processor) | In digital aids, turns the signal into numbers and decides how much to boost each pitch17 |
| Amplifier | Increases the power of the signal1 |
| Receiver | A miniature loudspeaker that delivers the sound into the ear canal7 |
| Battery | Powers the electronics: a disposable button cell or a rechargeable battery719 |
sound → microphone → chip → amplifier → receiver → ear
Most hearing aids today are digital.7 They turn sound waves into numbers, a bit like the binary code inside a computer. Because those numbers carry information about each sound's pitch and loudness, the aid can be programmed to boost some pitches more than others.1 In practice, most digital aids split incoming sound into several frequency bands, from low to high, and set a different amount of boost for each band, like the sliders on a music mixer.14
How much to boost each band comes from a hearing test. The aid is programmed to the degree and pattern of hearing loss the test finds.1615 Someone who misses high sounds gets a big boost in the high bands and little in the low ones.
Digital aids also give quiet sounds more help than loud ones. This is called compression. It matters because making a loud sound too loud is a bigger problem than making a soft sound a little too soft.14 That's why a hearing aid isn't just a volume knob: turning everything up equally would make the sounds a person already hears well uncomfortably loud.
All this happens fast. The processing delay has to stay tiny, because delays of just 3 to 6 thousandths of a second can be noticed.14
In the mixer toy above, the hearing patterns and bar heights are made-up examples to show the idea, not real hearing-test numbers.
| Digital | Analog | |
|---|---|---|
| How common | Most hearing aids today7 | Less common7 |
| How it handles sound | Turns sound into numbers; can boost some pitches more than others1 | Makes the continuous sound wave louder, amplifying all sounds in the same way7 |
| Extras | Noise reduction, directional focus, several programs7 | Some can store a few programs7 |
Hearing in background noise is one of the hardest jobs for a hearing aid, and it's the top complaint of many wearers.16 Digital aids use several tricks:
Wireless streaming often uses the same short-range radio as headphones; see how Bluetooth works. And if you're wondering how headphones cut noise with sound itself, that's a different trick: how noise cancelling works.
Hearing aids can help people hear sounds they've been missing, follow speech on the phone, and talk more easily with family and friends, even in noisy places.8 But they have limits:81
If a person has hearing loss in both ears, two aids are generally recommended: they give the brain a more natural signal and help with telling where sounds come from.1
| Style | Where it sits | Good to know |
|---|---|---|
| Behind-the-ear (BTE) | A case behind the ear, with a tube to an earmold or earpiece | Sturdy and easy to handle; often chosen for children; used for mild to profound loss71 |
| Receiver-in-canal (mini BTE) | A small case behind the ear, with the receiver in the canal | Smaller; can reduce a plugged-up feeling7 |
| In-the-ear (ITE) | A shell filling the outer part of the ear | Easier to handle than the tiniest aids7 |
| In-the-canal / completely-in-canal | Partly or fully inside the ear canal | Smallest and least visible, but harder to handle and adjust7 |
In the United States, adults 18 and older with perceived mild to moderate hearing loss can also buy over-the-counter (OTC) hearing aids without a prescription. Children and people with more severe hearing loss need prescription aids fitted by a hearing professional.96
A cochlear implant is a very different device. A hearing aid makes sound louder so damaged ears can detect it. A cochlear implant skips the damaged hair cells and sends electrical signals straight to the hearing nerve, which the brain learns to recognize as sound.310
| Hearing aid | Cochlear implant | |
|---|---|---|
| What it does | Amplifies sound into the ear canal | Turns sound into electrical signals for the hearing nerve3 |
| Uses the hair cells? | Yes, the ones that still work | No, it bypasses them10 |
| Parts | Worn in or behind the ear | An outside part (microphone, processor) plus an inside part placed under the skin by a surgeon3 |
| Usually for | Mild to severe hearing loss | People who are deaf or severely hard of hearing3 |
Neither device restores normal hearing, and hearing through an implant takes time and practice to learn.3 More than a million cochlear implants had been placed worldwide by 2022.5
Devices are a personal choice. Deaf communities are diverse, many Deaf people use sign language, and how someone identifies and communicates is up to them.17
Hair cells can't be replaced, so they're worth looking after at any age. Over a billion young people are at risk of hearing loss from listening too loud, for too long.12
Want to go deeper into the physics? See how sound travels, and for what's inside a rechargeable cell, how batteries work.
A microphone picks up sound and turns it into an electrical signal. A tiny computer chip turns that signal into numbers, uses settings from the wearer's hearing test to boost the pitches they hear less well, and an amplifier adds power. A tiny speaker, called the receiver, plays the adjusted sound into the ear canal. A battery powers it all.
Hearing aids don't restore normal hearing. They make sounds louder and clearer for the hair cells in the inner ear that still work. Many people hear much better with them, especially speech, but it can take several months for the brain to get used to the new sound.
They can make background noise louder along with the sounds you want, at first many sounds (even your own voice) can seem too loud, they can whistle if they don't fit well or are blocked by earwax, and they need batteries or charging, cleaning and occasional adjustment.
Neither is best for everyone. Behind-the-ear aids are sturdy, easy to handle and can give more power, so they suit many degrees of hearing loss and are often chosen for children. In-the-ear aids fill the outer bowl of the ear and are fairly easy to handle. In-the-canal aids are the smallest and least visible, but harder to handle and have less room for features. A hearing professional helps choose based on the kind of hearing loss and lifestyle.
A hearing aid makes sound louder so the ear's remaining hair cells can detect it. A cochlear implant skips the damaged hair cells and sends electrical signals straight to the hearing nerve. Implants are for people who are deaf or severely hard of hearing, for whom making sound louder isn't enough.
Most hearing aids today are digital. They turn sound into numbers, so they can be programmed to boost some pitches more than others, reduce steady background noise and focus on sound from the front. Analog aids, now less common, make all sounds louder in the same way.
In the United States, adults 18 and older with perceived mild to moderate hearing loss can buy over-the-counter (OTC) hearing aids in stores or online. Children and people with more severe hearing loss need prescription hearing aids fitted by a hearing health professional.