How does a cochlear implant (CI) work?

In a cochlear implant, the doctor surgically implants an electrical device in the inner ear that has a series of electrodes designed to stimulate the auditory nerve directly. After the ear has healed an external device, including a microphone and speech processor,is attached to restore some hearing. The process begins when sounds are detected by a microphone in the earpiece. The speech processor converts the sound waves into electrical signals and passes these along a wire to a transmitting coil that attaches behind the ear. The transmitter relays the signals through the skin to the implanted receiver, which transmits the electrical current down wires to electrodes in the cochlea. These electrodes stimulate the auditory nerve, which sends the signal to the brain. Sounds are divided into different groups based on their frequency or pitch. The device stimulates the proper electrode for that pitch. The stimulation intensity is varied by the loudness of the sound.