Optimisation in Signal and Image Processing

Chapter 13

Using Interactive Evolutionary Algorithms to Help Fit Cochlear Implants

13.1. Introduction

The surgical technique which enables profoundly deaf people with a fully functional cochlea to hear again was developed some 40 years ago [LOI 98]. During the surgical procedure, the surgeon inserts a very thin silicon filament which bears several electrode inserts, into the cochlea of the patients. The aim of this procedure is to stimulate the auditory nerve. The electrodes are connected to an antenna which is surgically placed under the skin, just behind the patient’s ear (see Figure 13.1).

In order to activate the electrodes, the patient wears a small apparatus called a BTE (for behind the ear) which looks like a hearing aid. The BTE is made up of two microphones that are connected to a digital signal processor (DSP) which transforms the received signal into electric pulses which are sent to the electrodes. The BTE is connected to a second exterior inductive antenna which works in collaboration with the antenna that is implanted under the patient’s skin, thanks to the use of a powerful magnet. The impulses that are emitted by the DSP are transmitted to the electrodes which have been implanted by the two inductive antennae (see Figure 13.1).

The objective of the interface that is created is to stimulate the auditory nerve with the aim of restoring the patient’s hearing to a certain level so that they are able to understand spoken language. The question of how to stimulate the ...