The implant sends sound waves into the auditory pathway after converting them into electrical energy. Today, in addition to numerous research institutions developing bionic hearing devices, several companies are already selling commercial products. Although there are differences in each product, they all work essentially the same way. Even in the profoundly deaf, at least one-third of the 30,000 fibers that stimulate the auditory nerve survive and are responsive, capable of transmitting to the brain's hearing center. Signals to this center are triggered by the cochlear implant.
Surgeons implant the device in the mastoid bone and inner ear through an incision behind the ear.
A small speech processor converts sound, picked up by an external mike, into an electrical signal. The signal is fed through the transmitter coil to the implanted receiver. Electrodes in the inner ear bypass the damaged area of the ear and create a nerve impulse that stimulates the auditory cortex of the brain. Artificial cochleas will not benefit all deaf people. Adults who have never heard are not suitable candidates, doctors say, because the auditory part of their brains will not respond to the stimuli.