A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or severely hard-of-hearing. The implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin. An implant has the following parts:

* A microphone, which picks up sound from the environment.
* A speech processor, which selects and arranges sounds picked up by the microphone.
* A transmitter and receiver/stimulator, which receive signals from the speech processor and convert them into electric impulses.
* An electrode array, which is a group of electrodes that collects the impulses from the stimulator and sends them to different regions of the auditory nerve.

An implant does not restore normal hearing. Instead, it can give a deaf person a useful representation of sounds in the environment and help him or her to understand speech.

In order to understand how the cochlear implant replaces missing sound, it is important to understand how we hear:

When sound waves reach your ear--for example, a doorbell or a car alarm or a crying baby--you know you've heard a soft sound or a loud sound. Your outer ear (the big flap you can see) collects sound and sends it into the middle ear. The sound waves bounce off your ear drum and are made louder by three tiny bones: the hammer, anvil, and stirrup. These are the smallest bones in your body. (Together they are smaller than an orange seed.) The sound waves travel into the inner ear. The inner ear is filled with fluid. The waves go through the cochlea (the organ of hearing), where tiny hair cells that can only be seen with a powerful electron microscope, pass on the vibration of the sound and turn it into electrical energy. Then your brain receives the energy and interprets or recognizes this energy as the "sound" of a doorbell or a car alarm or a crying baby.

So how does a cochlear implant work?

The cochlear implant takes advantage of the things an ear can still do after hair cells have been damaged or destroyed. It also takes advantage of how smart and flexible the human brain can be. The cochlear implant creates a new way of hearing. Here's how the implant works: A tiny microphone that is easy to wear captures the sounds of the doorbell, the car alarm, or a crying baby. The microphone collects and gives the vibrations of sound to a speech processor. The speech processor is a very complex electronic instrument that makes it possible to take the vibrations of speech and provide them to the auditory nerve as electronic signals. The implant is designed so that the nerve can use these electronic signals.

The reason the cochlear implant is called an implant is that a surgeon puts it under the skin behind the ear and into the skull. During surgery, the surgeon threads the implant into the cochlea (the special organ of hearing that looks like a snail's shell), past the damaged hair cells. That allows it to directly stimulate the auditory nerve that leads to the part of your brain that interprets sounds. The cochlear implant provides information that the brain can learn to understand--like a new code.

Many adult implant recipients report being able to function socially or vocationally in ways comparable to those with moderate hearing loss. Furthermore, they describe a new or renewed curiosity about the experience of hearing and the phenomena of sound. In some cases the experience of implantation becomes an integral part of the individual's identity, leading these implant users to participate and share experiences in support and advocacy groups. Many individuals may understand speech without lip-reading, may be able to make telephone calls, enjoy music, and can even watch television more easily.