cochlear implant

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An electronic apparatus that allows people with severe hearing loss to recognize some sounds, especially speech sounds, and that consists chiefly of a microphone and receiver, a processor that converts speech into electronic signals, and an array of electrodes that transmit the signals to the cochlear nerve in the inner ear.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A surgically implanted electronic device that can help provide a sense of sound to a person who is profoundly deaf or severely hard of hearing.