A cochlear implant is a surgically implanted medical device that is used to provide some sense of sound to persons who are profoundly deaf. Instead of amplifying sound like a hearing aid, the implant directly attaches wires to the cochlea to stimulate it based on environmental noise. The exterior of the device has a microphone, speech processor and radio frequency transducer. The interior has a coil which responds to the external transducer which relays the signals to the cochlea. It is generally only used in developed countries due to the cost of the device. In good cases, a deaf person can understand speech as long as the environment is quiet.