Simon King is Professor of Speech Processing at The University of Edinburgh, where he is director of The Centre for Speech Technology Research. His research spans speech synthesis, recognition and signal processing. Most of his current research focuses on creating more natural-sounding synthetic speech. Discovering the flaws in current ways of synthesising speech is an important step in this research, and of course this involves listening. Informal listening is a daily activity, but it is also very often formalised as listening tests in which non-specialists are asked to make judgements about certain properties of synthetic speech - such as rating their relative naturalness.