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Cochlear Implants

  1. Hugh J. McDermott

Published Online: 14 APR 2006

DOI: 10.1002/9780471740360.ebs0280

Wiley Encyclopedia of Biomedical Engineering

Wiley Encyclopedia of Biomedical Engineering

How to Cite

McDermott, H. J. 2006. Cochlear Implants. Wiley Encyclopedia of Biomedical Engineering. .

Author Information

  1. The University of Melbourne, Department of Otolaryngology, East Melbourne, Australia

Publication History

  1. Published Online: 14 APR 2006


Cochlear implants (CIs) are electronic systems that provide a partial replacement of the sense of hearing to people who have hearing impairment that cannot be alleviated adequately by means of conventional acoustic aids. In most cases of hearing loss, conventional aids that function principally as sound amplifiers are satisfactory. However, if the loss of hearing sensitivity in both ears is severe or profound, particularly across a wide range of frequencies, then amplification with conventional hearing aids may be inadequate. CIs have been developed to bypass the dysfunctional parts of the auditory system. They create hearing sensations by delivering electric stimuli directly to the auditory nerve via one or more electrodes located inside the cochlea (or inner ear). Recipients of CIs wear a device similar in appearance to an acoustic hearing aid on the external ear. This device contains a microphone, a signal processor, and a battery. In most existing CI systems, the external device transmits digitally encoded signals to an implanted receiver-stimulator via a pair of inductively coupled coils. The implanted device decodes these signals and generates precisely controlled pulses of current that are delivered to the electrodes to stimulate the auditory neurons. The patterns of current pulses are designed to represent selected components of the sound signal received by the microphone. Over the past 30 years, a considerable research effort has led to the development of various algorithms that convert sound signals into electric stimuli for CIs. The most successful of these schemes enable numerous CI users to understand speech and recognize many other types of sound by hearing alone, at least in favorable listening conditions. By the end of 2005, over 70,000 adults and children around the world were recipients of CI systems.


  • hearing;
  • deafness;
  • sensory prostheses