A cochlear implant is an electronic device that provides a sense of sound to individuals who are profoundly deaf or severely hard-of-hearing. Cochlear implants process sounds from the environment and directly stimulate the auditory nerve, bypassing damaged portions of the inner ear (NIH Fact Sheets). Cochlear implants require both an internal and an external device. The internal device is implanted surgically. The receiver sits under the skin on the base of the skull and is attached to an electrode array that is surgically inserted to the cochlea. The external component consists of a microphone and a computer (commonly called a sound or speech processor) that processes information. A transmitter on the external device is held in place against the skin by a magnet in the internal receiver.
A cochlear implant is different from a hearing aid in that it directly stimulating the auditory nerve. Traditional hearing aids amplify sound that the surviving part of the ear can still hear. For the profoundly hard-of-hearing, an implant is able to give the brain access to sounds that a hearing aid cannot provide.
The microphone is generally on the transmitter, which sends information to the processor and then to the receiver. Advanced Bionics uses a microphone that sits on the ear rather than on the transmitter. The basics way all implants work begins with sound being picked up by the microphone. Then, the processor filters and code the signal. The signal is sent through the cable to the coil. The signal is then sent via radio frequencies to the internal device. The electrodes are activated, and the coded electric signal is sent via the hearing nerve to the brain for interpretation.
Cochlear implant surgeries once destroyed all residual hearing in the implanted ear. New surgical techniques and softer electrode arrays preserve existing hearing at low frequencies, providing a truer representation of the original signal. To learn more about how implants work, understanding how the brain hears is necessary. The following link from the National Institute of Health is helpful.
Just as important as learning how the brain hears is understanding the importance of learning, the brain has to learn how to make sense of different information. Without rehab, training, and practice, it is possible for suboptimal outcomes if sounds aren’t meaningful for the user. Profoundly deaf children who receive a cochlear implant at a young age develop language skills at a rate comparable to children with normal hearing - but this does not happen automatically.