How does the ear work ?

The eardrum is connected by three small jointed bones in the air-filled
middle ear to the oval window of the inner ear or cochlea, a fluid-
filled spiral coil about one and a half inches in length. Over 10,000
hair cells on the basilar membrane along the cochlea convert minuscule
movements to nerve impulses, which are transmitted by the auditory
nerve to the hearing center of the brain.

The basilar membrane is wider at its apex than at its base, near the
oval window, whereas the cochlea tapers towards its apex. Different
groups of the delicate hair sensors on the membrane, which varies in
stiffness along its length, respond to different frequencies
transmitted down the coil. The hair sensors are one of the few cell
types in the body which do not regenerate. They may therefore become
irreparably damaged by large noise doses. Refer to the Tinnitus FAQ for
more information on hearing disorders.