A cochlear implant is a medical device that goes inside the cochlea, the spiral structure of three fluid-filled canals coiled up like a snail's shell in the inner ear. In one canal of the cochlea, there are hair cells along the length of the spiral. At the base of the spiral, the hair cells respond to higher frequencies and at the apex, they move at low frequencies. When these hair cells move, they trigger nerve cells that convert the sound wave to electrical impulses and passes the signal on to the brain for processing. Sensorineural hearing loss occurs when any part of this chain is not working as it does in a hearing person, and can be caused by many factors including age, loud noises, trauma, disease, or genetics. Sometimes a hearing aid is sufficient to treat sensorineural hearing loss, but when it is not, a cochlear implant may do the trick.
A typical cochlear implant consists of two parts: a speech processor and the implant itself. The speech processor sits on the back of the ear, taking in sounds and converting them to electrical signals, which are fed to the implant resting under the skin. The implant has a long array of electrodes that curls up inside the cochlea, which, when triggered, in turn disturb the nerve cells like the hair cells normally would. The brain can then interpret the electrical signals as sound. A cochlear implant unfortunately can't restore a full range of hearing just yet, and may not help make finer distinctions between the tones of speech and music. While there is debate over the usage of the devices in the deaf community, cochlear implants are still a marvel of science and technology.