Photo of Kenneth N. Stevens

Kenneth N. Stevens

  • National Medal of Science
  • Engineering

For his leadership and pioneering contributions to the theory of acoustics of speech production and perception, development of mathematical methods of analysis and modeling to study the acoustics of speech production, and establishing the contemporary foundations of speech science.

Have you ever wondered why languages use very similar vowel and consonant sounds? Kenneth N. Stevens, a scientist specializing in acoustic phonetics, studied linguistics and engineering to develop a theory to possibly explain this phenomenon.rnrnIn 1952, Stevens, along with three other scientists, hypothesized that human speech could be broken down into combinations of at least twenty distinctive features, such as the shape of the voice box, the tip of the tongue and placement of the lips. Initially, Stevens and his collaborators believed that small deviations in these articulators would have little effect on the sounds made. However, they quickly discovered that small differences in the positions of articulators made a big difference. This led to the creation of the quantal theory of speech, a formal equation that determines that the easier a sound is to pronounce, the more likely it is to show up in different languages across the world.rnrnNot only did the quantal theory of speech prove to be invaluable towards the development of speech recognition equipment, it also contributed towards the study of how sounds in languages are heard, known as speech perception. rnrnBy Kristen Brida