The middle ear is the air-filled chamber between the eardrum and the cochlea. It contains three tiny bones—the malleus, incus, and stapes—that transmit and amplify the vibrations of the eardrum to the oval window of the inner ear.

Sound waves striking the eardrum set it in motion. The ossicles act as a lever system that concentrates the force onto the much smaller oval window, matching the impedance of air to the impedance of the cochlear fluid. Without this amplification, most of the sound energy would be reflected rather than transmitted. The Eustachian tube connects the middle ear to the throat and equalizes air pressure on both sides of the eardrum.

Infections, fluid buildup, or fixation of the ossicles can produce conductive hearing loss. Surgical repair or amplification with hearing aids can often restore function when the middle-ear mechanism is impaired.

The middle ear is the mechanical bridge that carries airborne vibration into the fluid-filled inner ear.