He was Professor of Phonetics at University of California, Los Angeles (UCLA), where he taught from 1962 to 1991. His book A Course in Phonetics is a common introductory text in phonetics, and The Sounds of the World's Languages (co-authored with Ian Maddieson) is widely regarded as a standard phonetics reference. Ladefoged also wrote several books on the phonetics of African languages. Prior to UCLA, he was a lecturer at the universities of Edinburgh, Scotland (1953–59, 1960–1) and Ibadan, Nigeria (1959–60).
Peter Ladefoged was born on 17 September 1925, in Sutton (then in Surrey, now in Greater London), England. He attended Haileybury College from 1938–43, and Gonville and Caius College, Cambridge, Cambridge University from 1943–44. He received an MA (1951) and a PhD (1959) in Phonetics from the University of Edinburgh in 1959.
Ladefoged was involved with the phonetics laboratory at UCLA, which he established in 1962. He also was interested in listening to and describing every sound used in spoken human language, which he estimated at 900 consonants and 200 vowels. This research formed the basis of much of The Sounds of the World's Languages. In 1966 Ladefoged moved from the UCLA English Department to join the newly established Linguistics Department.
While at UCLA, Ladefoged was hired as a consultant on the movie My Fair Lady. He wrote the transcriptions that can be seen in Professor Higgins's notebook, and his voice was used in the scenes where Higgins describes vowel pronunciation.
Ladefoged was also a member of the International Phonetic Association for a long time, and was President of the Association from 1986 to 1991. He was deeply involved in maintaining its International Phonetic Alphabet, and was the principal mover of the 1989 International Phonetic Association Kiel Convention. He was also editor of the Journal of the International Phonetic Association. Ladefoged served on the board of directors of the Endangered Language Fund since its inception.
Ladefoged married Jenny MacDonald in 1953, a marriage which lasted over 50 years. They had three children: Lise Friedman, a bookseller; Thegn Ladefoged, archaeologist and professor of anthropology at University of Auckland; and Katie Weiss, attorney and public defender, residing in Nashville, Tennessee. He also had five grandchildren Zelda Ladefoged, Ethan Friedman, Amy Friedman, Joseph Weiss, and Catherine Weiss.
On May 5, 1970, Ladefoged was arrested and suffered injuries from police while participating in an anti–Vietnam War protest at UCLA. He was initially charged with failure to disperse, but the charge was later changed to assault on a police officer. He was acquitted in the first trial.