Sound processorWorn behind the ear. It turns sound into a signal.
MicrophoneIt picks up sound from around the wearer.
TransmitterIt sends the signal through the skin to the implant.
MagnetIt holds the transmitter on the head, over the implant.
BatteryIt powers the outside parts.
Under the skin 5
SkinThe implant lies under it. The transmitter rests on it.
Receiver-stimulatorIt receives the signal and turns it into electric impulses.
Electrode arrayA strip of electrodes inside the cochlea. It passes the impulses on.
CochleaThe coiled part of the inner ear.
Auditory nerveIt carries the signals from the cochlea to the brain.
How this list was compiled: Every name checked on 2026-09-30, a name kept only where two of these use it: (1) National Institute on Deafness and Other Communication Disorders (NIH), Cochlear Implants, https://www.nidcd.nih.gov/health/cochlear-implants (an external portion behind the ear and a portion placed under the skin; a microphone, a speech processor, a transmitter and receiver/stimulator, an electrode array; signals sent by way of the auditory nerve to the brain; the cochlea); (2) US Food and Drug Administration, What is a Cochlear Implant? and Benefits and Risks of Cochlear Implants, https://www.fda.gov/medical-devices/cochlear-implants/what-cochlear-implant and https://www.fda.gov/medical-devices/cochlear-implants/benefits-and-risks-cochlear-implants (the externally worn microphone, sound processor and transmitter system; the implanted receiver and electrode system; a magnet that holds the external system in place next to the implanted system; the inner ear and the auditory nerve; batteries); (3) Wikipedia, Cochlear implant, text only, https://en.wikipedia.org/wiki/Cochlear_implant (the sound processor contains microphones, electronics, a battery and a coil that signals the implant through the skin, held in place by magnetic attraction; a receiver/stimulator; an electrode array embedded in the cochlea; the cochlear nerve). Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; no photograph or plate followed. Licence: own work
How it works
A cochlear implant has an outside part, worn behind the ear, and an inside part under the skin. Two drawings give the names only: five parts outside, then the parts under the skin and the ear parts they meet.
Read the full guide
Follow the signal
Sound reaches the microphone on the sound processor, which runs on a battery. The processor passes a signal to the transmitter, held on the head by a magnet. Under the skin, the receiver-stimulator takes the signal and turns it into electric impulses. They travel along the electrode array, which lies inside the cochlea, and reach the auditory nerve.
Sound processor and speech processor are two names for the same part.
This page names parts only. It is not medical advice.
Questions and answers
What are the main parts of a cochlear implant?
An outside part and an inside part. Outside are a microphone, a sound processor and a transmitter. Inside, under the skin, are a receiver-stimulator and an electrode array.
What holds the outside part of a cochlear implant on the head?
A magnet. The transmitter has a magnet that holds it on the head, next to the implanted part under the skin.
What is the electrode array?
A group of electrodes on a thin strip that lies inside the cochlea. It collects the electric impulses from the receiver-stimulator and sends them to the auditory nerve.
Is a cochlear implant the same as a hearing aid?
No. A hearing aid is worn whole, on or in the ear. A cochlear implant has a second part under the skin: a receiver-stimulator, with an electrode array inside the cochlea.