Cochlear implant. Illustration of a cochlear implant in a human ear. This device transmits electrical impulses directly to sensory cells in the cochlea (coiled structure on right) to restore some degree of hearing in the severely deaf. A microphone fitted in the outer ear converts sound waves into an electrical signal, which then passes to a transmitter on the skin over the ear. This sends the signal through the skin to a surgically implanted receiver directly underneath, from which the signal passes along a wire to electrodes implanted in the cochlea. Cochlear implants enable the user to hear the rhythms of speech, improving understanding through lip-reading.