Kenneth ‘Ken’ Stevens (March 23, 1924 – August 19, 2013) was a Professor of Electrical and Computer Science at the Massachusetts Institute of Technology (MIT) known for his pioneering work in acoustic phonetics. Stevens completed his SB and SM in engineering physics at the University of Toronto in 1945, and his ScD in electrical engineering at MIT in 1952. His doctoral advisor at MIT was the renowned acoustician Leo Beranek, and his dissertation was devoted to the perception of sounds shaped by resonance circuits, where he demonstrated that autocorrelation could be used to discriminate vowel sounds. He joined the MIT faculty in 1954 and continued there until his retirement in 2007, at age 83.

In his early years at MIT, Ken Stevens started a long-term collaboration with Gunnar Fant on the development of a transmission-line model of the vocal tract and the analysis of speech sounds and their physical properties. This modeling approach has been fundamental for describing the articulatory control of the vocal tract and the understanding of the subglottal system, and it continues to be a foundational tool in voice production research. His theoretical work on acoustic properties of speech sounds that comprise the linguistic elements of language form the major principles of speech science. His quantal theory of speech production posits that certain articulatory movements produce stable acoustic outputs, leading to distinct and consistent speech sounds across languages. This stability results from the non-linear relationship between articulatory gestures and the acoustic spectrum. Thus, small changes in articulation can lead to significant acoustic variations, except at these “quantal” points, which correspond to the sounds that are most frequently used in languages worldwide, thus forming a universal basis for phonetic categories. His subsequent work used these principles to describe acoustic invariance and a model of human lexical access (see figure from Stevens, 2002, https://doi.org/10.1121/1.1458026) that integrated major portions of acoustic phonetics, phonology, speech science and linguistics.

Ken Stevens received numerous awards throughout his career, including the National Medal of Science (1999), the Silver Medal in Speech Communication (1983) and Gold Medal (1995) from the Acoustical Society of America (ASA), and the James L. Flanagan Speech and Audio Processing Award (2004) from the Institute of Electrical and Electronics Engineers (IEEE). He was a fellow of the American Association for the Advancement of Science, the IEEE (Life Fellow), and the ASA, where he served as President in 1976. He was also known for his profound impact on students and colleagues, generously offering support and guidance to numerous researchers in the field of speech science. He was the doctoral advisor of many prominent speech scientists, including James Flanagan, Joe Perkell, Lawrence Rabiner, Victor Zue, Abeer Alwan, Carol Espy-Wilson, and George Wodicka (my PhD advisor), to say a few, and mentored and collaborated with many others such as Dennis Klatt, Alan Oppenheim, and Stefanie Shattuck-Hufnagel. Ken Stevens was my “grand PhD advisor,” and I had the privilege of interacting with him during a few visits to MIT. All the praise I had heard about him was accurate: he was exceptionally kind and welcoming. Our technical yet deeply philosophical conversations about electrical engineering and speech science profoundly influenced me, so much so that I named my first laboratory in his honor.

Matías Zañartu, Ph.D.