A sound wave is a vibration in the air that enters the ear canal. The sound strikes the eardrum, causing it to vibrate. Behind the vibrating eardrum, in the middle ear, are three small bones that move in response to the eardrum. These bones transfer the vibrations to the cochlea, traveling through the cochlear duct toward the auditory nerve. Nerve impulses travel to the brain, which translates them into a sound you can understand.