E ear A component of a complex acoustical system of hearing. Three main parts of the human ear are the outer ear, the middle air, and the inner ear. The outer ear consists of the pinna and the auditory canal which is closed at the end by the eardrum. The middle ear has three small bones: the hammer, the anvil and the stirrup, which are connected to each other. The hummer and the stirrup are attached to the eardrum and to the oval window, respectively. The oval window is a membrane that divides the middle ear from the inner ear, which consists in part of the cochlea and the basilar membrane. A sound from the outer ear sets the eardrum into vibrations. These vibrations are further transmitted through the bones of the middle ear to the oval window and the basilar membrane, which has nerve endings connected to the brain. This process results in the hearing of sound. Human ears can localize a source of sound and distinguish its loudness, timbre and pitch. See also audibility, limits of; audio frequency; binaural.