William J. Hardcastle is Emeritus Professor of Speech Sciences at Queen Margaret University, Edinburgh. He is a Fellow of the British Academy and the Royal Society of Edinburgh, and an Honorary Fellow of the Royal College of Speech and Language Therapists. He has published numerous books and articles in different areas of speech science, including the mechanism of speech production and sensory-motor control in normal and pathological speech, and is the author of Physiology of Speech Production (1976) and Disorders of Fluency and their Effects on Communication (with P. Dalton, 1989).

John Laver is Emeritus Professor of Speech Sciences at Queen Margaret University, Edinburgh, where he was Deputy Principal. He is a Fellow of the British Academy and the Royal Society of Edinburgh. He was appointed CBE in 1999 for contributions to phonetics, and has been President of the International Phonetic Association (1991-95). His publications include The Phonetic Description of Voice Quality (1980), Principles of Phonetics (1994), and The Gift of Speech (1996). He is currently co-authoring The Encyclopedic Dictionary of Speech and Language (forthcoming, Wiley-Blackwell).

Fiona E. Gibbon is Head of the Department of Speech and Hearing Sciences at University College Cork in Ireland. She is a Fellow of the Royal College of Speech and Language Therapists, and her research was awarded the Queen’s Anniversary Prize for excellence in 2002. She has published over seventy book chapters and papers in professional and scientific journals, and is co-editor of Vowel Disorders (2002).