What does the cochlea do?
General information only. This article explains the basics and is not medical advice. For anything about your own health, talk to a doctor or other qualified professional.
Quick answer
The cochlea is the snail-shaped, fluid-filled part of the inner ear that turns sound into signals the brain can understand. It sits inside the bony labyrinth of the temporal bone, next to the vestibular system, which controls balance. Tiny hair cells inside it convert vibrations into nerve impulses.
The ear in three parts
| Part | Main structures | Job |
|---|---|---|
| Outer ear | Ear flap, ear canal | Collects sound |
| Middle ear | Eardrum and three tiny bones | Amplifies vibrations |
| Inner ear | Cochlea and vestibular system | Hearing and balance |
The inner ear is called the labyrinth because of its maze of tubes and chambers. Its two main sections are the cochlea for hearing and the vestibular system (three semicircular canals plus the utricle and saccule) for balance.
How the cochlea turns sound into signals
- Sound vibrates the eardrum and the middle-ear bones; the last one, the stapes, pushes on a membrane called the oval window. See the smallest bone in the human body.
- This creates waves in the fluid inside the cochlea.
- The waves move the basilar membrane, which runs along the cochlea’s coil.
- About 15,000 hair cells sitting on it bend, opening tiny channels that create electrical signals.
- The auditory nerve carries these signals to the brain.
Built like a piano keyboard
Different parts of the cochlea respond to different pitches. The base, near the entrance, picks up high sounds; the tip of the coil picks up low sounds. Unrolled, the cochlea would be about 3.5 cm long.
Hair cells don’t grow back
Humans can’t regrow damaged cochlear hair cells. Loud noise and aging can harm them over time, which is a common cause of hearing loss. Protecting ears from very loud sounds helps preserve them.
Cochlear implants
A cochlear implant is an electronic device that bypasses damaged hair cells and stimulates the auditory nerve directly. It can help many people with severe hearing loss to perceive sound.
The balance part of the inner ear works with the brain; see what part of the brain controls balance.
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