The ear is composed of three main parts: the outer ear, the middle ear, and the inner ear. The outer ear consists of the Pinna and the ear canal. The pinna collects sound and the ear canal connects the outer and middle ear. Sound must move through the canal to reach the middle ear. The middle ear consists of the ear drum and the 3 tiny bones also known as the ossicles. The ossicles are the malleus, incus, and stapes. The ear drum receives the sound waves and moves around, also causing the ossicles to move. The sound wave at this point becomes a vibration. The inner, also known as the cochlea, holds the fluids endolymph and perilymph and contains the corti organ, which is the sensory receptor. The cochlea holds the hair cells that receive the nerves for hearing. The vibration of sound moves the fluids in the inner ear that in turn stimulate the hair cells. Hair cells have certain frequencies they respond to, so only certain hair cells may be stimulated. The movement's signal is turned into nerves and sent to the brain through the auditory nerve to the hearing section of the brain, the auditory cortex.
Source: http://www.asha.org
Source: http://www.asha.org