William J. Hardcastle is Professor of Speech Sciences and Head of the Department of Speech and Language Sciences at Queen Margaret College, Edinburgh. From 1974 until 1993 he worked in the Department of Linguistic Science at Reading University where he was Professor of Speech Science and Director of Speech Research Laboratory. He has published books and articles in a number of different areas of speech science including the mechanisms of speech production and sensori-motor control in both normal and pathological speech. He is Fellow of the Institute of Acoustics and has been President of the International Association of Clinical Phonetics and Linguistics since 1991.

John Laver is Professor of Phonetics at the University of Edinburgh, where he was Vice-Principal of the University with Special responsibility for research from 1994 to 1997. He was the founding Chairman of the Humanities Research Board of the British Academy from 1994 to 1998, and is Fellow of the British Academy, the Royal Society of Edinburgh and the Institute of Acoustics. He has held visiting posts at the University of California at Los Angeles, and at Macquarie University, Australia. He was the President of the International Phonetic Association from 1991 to 1995. He has published widely in phonetics, speech science and speech technology, and is the author "The Phonetic Description of Voice Quality" (1980); "The Gift of Speech" (1991); and "Principles of Phonetics "(1994).