Professor Clark has devoted all his efforts, for the past 30 years, to development of an effective cochlear implant system to bring hearing to profoundly deaf children. His early research into the electrical transduction properties of the cochlea established the need for a multi-channel multi-electrode system based upon formant analysis of speech signals. This system, developed in collaboration with electrical engineers and other specialist colleagues, has been remarkably successful, and gives speech recognition ability even to children who have been profoundly deaf since birth. The device, which continues to be improved, has been implanted into more than 15 000 people worldwide.