American scientist Dennis Klatt pioneered synthesised speech in the 1980s. He used recordings of himself to make the sounds that gave British physicist Stephen Hawking a voice when he lost the ability to speak. Friend and colleague of Dr Klatt, Joseph Perkell, told Rebecca Kesby about the man who gave his voice to Prof Hawking allowing him to educate the world in science.

(Photo: BOMBAY, INDIA: World-renowned physicist Stephen Hawking answers questions with the help of a voice synthesiser during a press conference at the Tata Institute of Fundamental Research (TIFR) in Bombay, 06 January 2001. Credit AFP)