Pitch Continuity and Speech Source Attribution

Two experiments showed that continuity of the pitch contour is an important perceptual indicator that a formant pattern comes from a single speech source. Subjects listened to repeatedly played formant patterns that changed smoothly between two vowels. When the pitch was a monotone, these patterns were heard as containing semivowels and liquid consonants; but when a discontinuous, steplike pitch contour was imposed on the patterns, they divided into two perceptually distinct speech sources, and the phonemic percept changed to a predominance of stop consonants. In the second experiment, this effect was shown to be due to changes in pitch itself, rather than to concomitant changes in amplitude or energy. Earlier suggestions that continuity of both formant structure and pitch contour are important for the perceptual coherence of speech were borne out.