Question

1. Briefly describe three different sound processing schemes used to modify received sound signals before they are sent to a cochlear implant.

Answer 1

First, let us understand what a cochlear implant is?

These are the first examples of neural prosthesis that can substitute a sensory organ. They bypass the malfunctioning auditory periphery of profoundly-deaf people to electrically stimulate their auditory nerve.

Now the implant consists of three major architecture and functional blocks.

1. An external unit (aka Speech processor) consists of a DSP (digital signal processor), a power amplifier and an RF transmitter.

2. An internal unit consists of the RF receiver and a hermetically sealed stimulator.

3. And an electrode array connected to the cochlea to stimulate the auditory nerve.

Now, the sound processing schemes are as follows before the signal reaches the cochlea

1. The behind-the-ear external processor with ear hook and a battery case uses a microphone to pick up sound, converts the sound into a digital signal.

2. The DSP processes and encodes the digital signal into a radio frequency (RF) signal, and send it to the antenna inside a headpiece.

3. The headpiece contains active electronic circuits that derive power from the RF signal, decode the signal, convert it into electric currents, and send them along wires threaded into the cochlea.

4. The electrodes at the end of the wire stimulate the auditory nerve connected to the central nervous system, where the electrical impulses are interpreted as sound.