Sound waves are collected by the outer ear and channeled along the ear canal to the eardrum. The impact of sound hitting the eardrum creates vibrations that cause three bones in the middle ear — the malleus, incus, and stapes (hammer, anvil and stirrup) — to move. The smallest, the stapes, fits into the oval window between the middle and inner ear. When the oval window vibrates, fluid in the inner ear transmits the vibrations into the hearing organ, called the cochlea.

In the inner ear, thousands of microscopic hair cells are bent by the wavelike action of fluid inside the cochlea. The bending of these hairs sets off nerve impulses that are then passed through the auditory nerve to the hearing center of the brain. This center translates the impulses into sounds the brain can recognize.