How Do Humans Hear?

The human ear consists of three main parts: the outer ear, middle ear, and inner ear.  

The outer ear consists of the pinna and external auditory canal up to the eardrum. Sound waves are funneled by the pinna down the auditory canal where they vibrate the eardrum.  This in turn vibrates the three bones of the middle-ear, the malleus, incus, and stapes, otherwise known as the ossicles.   These ossicles act as a lever system that transmits vibrations to the inner ear which consists of a spiral-shaped fluid-filled cavity called the cochlea.  As the lever system of the middle ear vibrates, the footplate of the stapes pushes into the cochlea and creates a pressure wave within the fluid. This wave stimulates membranes that contain tiny hair-cells.  These hair cells then create action potentials that are sent to the hearing nerve (8th nerve) up to the brain where sound is processed.