How hearing aids are made
A hearing aid is a microphone, a tiny computer and a speaker, usually run on a zinc-air button cell or a small rechargeable.
- stations
- 6
- things upstream
- 75
- raw sources
- 24
- steps from the ground
- 9
The short version
A hearing aid is a small computer that picks up sound, processes it and replays it louder. Its chip, microphones and receiver are mounted on a small circuit board. That board and a battery drawer fit inside a molded plastic case, or a custom shell made from a scan of the wearer's ear. The unit is then programmed and tested.
-
Print the circuit board
A thin flexible board is etched with copper tracks that link every component. It is only a few millimeters across in the smallest models.
Goes in -
Place the chip
A signal-processing chip, which splits sound into frequency bands and amplifies each one, is soldered onto the board along with capacitors and tiny resistors.
-
Fit the microphones
Miniature microphones are attached to pick up sound, often in pairs so the device can favor sounds coming from the front. A receiver, the tiny loudspeaker, is wired in too.
-
Mold the case
Plastic cases are injection molded. Custom in-the-ear shells are instead built from a scan of the wearer's ear canal so they fit exactly.
Goes in -
Add the battery drawer
A battery door holds a button cell, usually a zinc-air type that draws oxygen from the air once its sealing tab is removed. Rechargeable models use a sealed cell instead.
Goes in -
Program and test
An audiologist's software tunes the amplification to the wearer's hearing test. The unit is then run through acoustic tests inside a sound-proof chamber.
Worth repeating
- The transistor, invented in 1948, suited hearing aids well because it needed little power and was small, and hearing aids were early adopters.
- Most modern hearing aids use one of five standard sizes of zinc-air button cell battery.
- Small sound amplifiers sold to consumers cannot legally be called hearing aids, which are medical devices in most countries.
Back to the ground
Follow every input upstream and hearing aid starts as these 24 raw sources.
Everything it is made of See it on the map
Open the whole family tree
Keep walking
Sources
Cite this page: "How hearing aids are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/hearing-aid