A cochlear implant is an electronic device used by some people who have a hearing loss. It artificially stimulates the auditory nerve to create the sensation of sound. This can be sufficient for the implantee to "hear" well enough for them to learn to listen and speak in the hearing world. Typically, only those with a severe or profound hearing loss will use cochlear implants as those with less severe losses are able to obtain a sufficient level of hearing using traditional hearing aids.
How cochlear implants work
An implant consists of four main components. A sensitive microphone, which sits behind the ear, collects sound and converts it to an electronic signal. This signal is received by the speech processor - a small computer that sits behind the ear or, in older models, in a body-worn pouch. The speech processor converts the original signal to a number of separate signals, each of which corresponds to a different band of frequencies. These signals are sent to a transmitter on the head and by the transmitter across the skin to the implanted electrodes in the cochlea. Each signal from the speech processor is sent to a different electrode, and each electrode is placed at a different point in the cochlea. The brain interprets the signal at each different point in the cochlea as being of a different frequency, thus replicating the original sound picked up by the microphone.
Cochlear implants do not restore normal hearing, and the benefit will vary between recipients. Factors that can affect the amount of benefit include the age of the recipient, how long the recipient has been deaf and the quality of the auditory nerve.
The total cost of a cochlear implant including evaluation, surgery, the device, and rehabilitation is around $40,000. Cost is therefore a significant factor in restricting the uptake of implants where potential recipients do not have access to funding from insurance companies or government health programs.
- American Academy of Otolaryngology http://www.entnet.org/healthinfo/ears/cochlear-implant.cfm