Cochlear implant. Computer artwork of a section through the outer (left) and inner (right) ear showing a cochlear implant (top left), a prosthetic hearing device. Sound from an external microphone (behind external ear, top left) is transmitted (red lines) to an electrode (dotted curled line, right) implanted in the cochlea (pink, coiled, right) of the inner ear. The electrode transmits the sound as electrical impulses to the auditory nerve, allowing the person to hear the sounds.