What is a Cochlear Implant?
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A cochlear implant is an artificial hearing device, designed to produce useful hearing sensations by electrically stimulating nerves inside the inner ear.
A cochlear implant comprises two separate parts:
1. An internal implant device: The receiver-stimulator contains electronic circuits that control the flow of electrical pulses into the ear. Attached to the package is the 22 electrode array, which is inserted into the shell-like structure in the inner ear known as the cochlea.The entire device (shown Right) is placed under the patient's skin, behind the ear, during an implant operation. |
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2. An external sound processor The sound processor sits behind the ear and is worn externally, similar to a hearing aid.
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How does a Cochlear Implant work?
Speech and other sounds in the environment are picked up by the external microphones and sent to the sound processor. The processor codes the sounds into an electrical signal. This electrical signal is then sent by the transmitting coil, through the skin to the implant, which changes the signal to electrical pulses. The pulses pass through the electrode array and stimulate hearing nerve fibres directly within the cochlea.
What does it sound like?
It is not possible to make sounds completely natural, because the cochlear implant uses 22 electrodes to replace the function of tens of thousands of hair cells in a normally hearing ear.
A cochlear implant does not just make sounds louder as does a hearing aid. Instead, it selects out some of the important information in the speech signal and then produces a pattern of electrical pulses in the recipient’s ear.
This pattern is selected to sound as close as possible to the original speech sound.
