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Cochlear ImplantsA cochlear implant bypasses missing or damaged sensory cells in the inner ear to directly stimulate the auditory nerve. The device includes an external microphone worn behind the ear, a sound processor, and transmitter. The transmitter delivers electrical stimulation to a receiver implanted beneath the skin, which relays the signals along an implanted electrode to the inner ear, or cochlea. Typically, eight electrodes are used to deliver eight different frequencies of sound. Since sounds heard through a cochlear implant do not recreate the subtleties of normal hearing, surgical implantation is followed by significant therapy to train users to interpret the sounds. Many users are eventually able to follow conversation unaided. Commercially available since the 1980s, cochlear implants have been used by about 219,000 people worldwide. |