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Cochlear Implant

What Is A Cochlear Implant?

A cochlear implant is a medical device designed to improve speech perception for people with severe to profound hearing impairment.

A cochlear implant is also useful for people who do not obtain good benefit from an acoustic hearing aid. 

Cochlear implants have been used since the 1970s, and there are now a million cochlear implant users around the world. 


Watch a 2 minute video on our hearing therapeutics research

The Bionics Institute was founded by Professor Graeme Clark, leader of the team that created Australia’s cochlear implant at the University of Melbourne. In 1978, Rod Saunders was the first person to receive a cochlear implant at the Royal Victorian Eye and Ear Hospital. 

Then called the Australian Bionic Ear and Hearing Research Institute (ABEHRI), the institute opened its doors in 1986 and undertook research to improve the cochlear implant. Commercialised by Cochlear Ltd, the cochlear implant has given hearing to more than 600,000 people with hearing impairment around the world.

Since 2011, Bionics Institute researchers have developed medical devices to change the lives of people living with hearing impairment, vision loss, epilepsy, Parkinson’s disease, rheumatoid arthritis, type 2 diabetes and Crohn’s disease.

The following steps are needed for effective hearing [1]:

  1. Sound waves travel down the ear canal to the eardrum causing it to vibrate.
  2. These vibrations pass to three small bones (ossicles) and are transmitted across the middle ear.
  3. The vibrations move into the fluid of the cochlea in the inner ear and cause tiny rippling waves.
  4. Hair cells on the cochlea’s elastic membrane are moved by the rippling fluid, opening microscopic channels.
  5. Chemicals flow through the channels into the hair cells and cause the release of a neurotransmitter (chemical messenger) which results in an electrical signal being generated.
  6. The auditory (hearing) nerve transmits the electrical signal to the brain for processing in a complex series of relay stations, which results in hearing.

As long as the auditory nerve and the part of the brain that processes sound are working, the cochlear implant can bypass the damaged part of the ear.

In normal hearing, hair cells in the inner ear transmit vibrations due to sound to the hearing nerves in the inner ear, which then, in turn, transmit the sound signal to the brain.

A cochlear implant replaces the function of the hair cells in the inner ear, which are damaged or lost in the case of a severe hearing impairment.

Small electrodes are placed in the inner ear, which activate the hearing nerve using small pulses of electrical current.

An external sound processor is worn like a hearing aid behind the ear or on the scalp. This processor encodes the sound and transmits instructions to the implanted electronics (called the receiver/stimulator), which activates the electrodes in a specified pattern to activate the hearing nerve.

Anyone who does not get enough benefit from a hearing aid can benefit from a cochlear implant as long as they have an inner ear suitable for the device, and a viable hearing nerve. Some other important factors are described in Table 1.


Possible factors affecting cochlear implant suitability and benefits [2–4]

  • Age limitations depend on the country but are generally between six months and no upper age limit, provided general health is considered
Hearing loss in one or both ears
  • Children five and over with profound one-sided hearing loss may be suitable for cochlear implantation
  • If there is profound hearing loss in one or both ears, for over 10 years, implantation may be less useful
Hearing loss onset before or after speech development (approximately two years of age)
  • Research has shown that adults who receive cochlear implants after speech attainment have better speech perception than those whose hearing loss occurred before speech attainment
Adults who have very poor speech perception
  • This group may have a significantly greater improvement than those with mild speech perception problems
Adults in general
  • Researchers found they reported a 12% improvement in general quality of life
Past response to hearing devices
  • A failed trial of hearing aids for a number of months is usual before implantation is considered
Country’s medical device regulator, cochlear implant manufacturer variability
  • These influence suitability for implantation

Cochlear implants are usually implanted under general anaesthesia. The procedure is followed by implant activation, specialist support to optimise the implant and intensive rehabilitation. Any medical procedure has its risk and these should be discussed in detail with the surgeon before going ahead.

New tests and management options under development at the Bionics Institute

Deep expertise in hearing research at the Bionics Institute has given rise to ground-breaking tests and new management options:

• Research to develop ways to individually optimise the benefits gained from cochlear implants

• A new infant hearing test that images the brain using near-infrared light to give children with hearing impairment the best chance to hear and speak.

• A world-first test for tinnitus that can diagnose presence and severity of tinnitus with high accuracy

• Research into the genetic modification of nerve cells to respond to light and electricity to combat the issue of current spread in cochlear implants

• Development of therapeutics using nanotechnology to restore age-related hearing impairment.

With your help, we can accelerate the evolution of this research, improving the lives of people with hearing impairment.

Read more about our hearing research here.

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Medical disclaimer

This article contains general information relating to a medical condition. Such information is provided for informational purposes only and does not replace medical advice given by your healthcare professional.


1. Age-Related Hearing Loss [Internet]. Source: NIDCD. 2022 [cited 2022 May 5]. Available from:

2. Cochlear Implants [Internet]. Source: NIDCD. 2021 [cited 2022 May 10]. Available from:

3. Rauterkus G, Maxwell AK, Kahane JB, Lentz JJ. Conversations in Cochlear Implantation: The Inner Ear Therapy of Today. (CC BY). Biomolecules [Internet]. 2022;12:1–18. Available from:

4. Boisvertid I, Reis M, Au A, Cowan R, Dowell RC. Cochlear implantation outcomes in adults: A scoping review. (CC BY 4.0). 2020;15(5):1–26. Available from:

5. FDA. Benefits and Risks of Cochlear Implants [Internet]. 2021 [cited 2022 May 15]. Available from:

6. Swaddiwudhipong N, Jiang Y, Landry G, Bance Y. Investigating the Electrical Properties of Different Cochlear Implants. (CC BY 4.0). Otol Neurotol 4259–67,. 2021;42:59–67.