From Wired by Joao Medeiros.
Hawking is very attached to his voice: in 1988, when Speech Plus gave him the new synthesizer, the voice was different so he asked them to replace it with the original. His voice had been created in the early ‘80s by MIT engineer Dennis Klatt, a pioneer of text-to-speech algorithms. He invented the DECtalk, one of the first devices to translate text into speech. He initially made three voices, from recordings of his wife, daughter and himself. The female’s voice was called “Beautiful Betty”, the child’s “Kit the Kid”, and the male voice, based on his own, “Perfect Paul.” “Perfect Paul” is Hawking’s voice.