The Difference between Hearing Aids and Cochlear Implants

Cochlear implants work very differently from hearing aids:

• Hearing aids amplify sound. A cochlear implant, on the other hand, transforms speech and other sounds into electrical energy that is used to stimulate surviving auditory nerve fibers in the inner ear.
• Unlike most hearing aids, cochlear implants have both internal and external components. A surgical procedure is needed to place the internal processor component of the implant.

Hearing aids send amplified sound through both the outer and middle ear and finally to the sensory receptor cells, (commonly called hair cells) in the inner ear. The function of the hair cells is to change (transduce) the sound energy into electro-chemical signals that are recognized by the hearing nerve. When hair cells are damaged or dead, parts of the signal may be distorted, or may not be sent to the hearing nerve at all. Since hair cell damage is by far the most common cause of hearing loss, cochlear implants bypass the damaged hair cells and replace their function by converting sound energy into electrical energy that can directly stimulate the auditory nerve. The nerve recognizes this stimulation in much the same way normal sound is recognized, and the information is sent along the nerve to the brain where meaning is attached.

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