Sound normally moves into the ear canal and makes the eardrum vibrate. At a structure known as the umbo, the eardrum connects to a chain of three tiny bones-the hammer, anvil and stirrup-that vibrate. The stirrup touches the cochlea, the inner ear's fluid-filled chamber, and hair cells on the cochlea's inner membrane move, triggering the release of a neurotransmitter chemical that carries the sound signals to the brain.

In profoundly deaf people the hair cells don't work. So in a traditional cochlear implant, the microphone, signal processor and transmitter coil, which are worn outside the head, send signals to a receiver-stimulator under the skin, which then sends the signals to electrodes implanted in the cochlea and stimulates auditory nerves. The ear canal, eardrum and hearing bones are bypassed.

The system developed in Utah moves all the external components inside the body. Sound moves through the ear canal to the eardrum, which vibrates as it does normally. An accelerometer is attached to the umbo to detect the vibration. The accelerometer is also attached to a chip, and together they serve as a microphone that picks up the sound vibrations and converts them into electrical signals sent to the electrodes in the cochlea.

The package is glued to the umbo so the accelerometer vibrates in response to eardrum vibrations. The moving mass generates an electrical signal that is amplified by the chip, which then connects to the a speech processor and stimulator wired to the electrodes in the cochlea.