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How does a cochlear implant work?

Photo: Cochlear implants can provide a sensation of hearing

Instead of simply making sounds louder (as with a conventional hearing aid), a cochlear implant provides a sensation of hearing by bypassing the damaged hair cells in the cochlea and directly stimulating the auditory nerves by using electrical signals.

Cochlear implants work in the following way:

  • The microphone of the cochlear implant picks up the sound and the speech processor converts the sound waves into a digital code which is then sent to the transmitter coil.
  • The transmitter coil sends the coded signal through the skin to the implanted receiver which is located just under the skin. The receiver converts the digital code to an electrical signal. This signal is then sent from the implanted receiver via a wire to the electrodes in the cochlea.
  • The electrodes stimulate the cochlear nerve fibres and they send the signal to the brain.
  • The brain interprets these signals so the wearer can understand what was heard.

Diagram 1: Parts of a cochlear implant

Diagram 2: Cochlear implant in place

What does the world sound like through cochlear implants?

The sound perceived through a cochlear implant is not the same as the sound heard with normal hearing. Cochlear implant wearers who have previously heard naturally often describe the sound as being robotic or tinny. However, with time the brain adjusts to the new signals and what is heard becomes more natural.

We can’t know exactly what the world sounds like to someone using a cochlear implant, and it will of course vary between people, but there are some simulations available.

The University of Southampton Auditory Implant Service offers simulations of different voices and music, and a link to the University of Granada, Spain where you can download a program to make your own simulations of sound perception through a cochlear implant.