The acoustics of gestural overlap
Khalil Iskarous · The Journal of the Acoustical Society of America · 2001
Acoustic modeling of speech production focuses on the effects of a single tongue constriction and a simultaneous labial constriction on the formant frequencies of an acoustic tube. But research on dynamic speech production reveals that tongue gestures overlap in time, so two or more simultaneous tongue constrictions affect the acoustic output of the tube. Understanding the acoustics of natural speech therefore requires an investigation of the acoustic effects of multiple constrictions. The goal is to generate a generalized formant nomogram that would reveal how the acoustic effects of single constrictions combine and interact in determining the acoustic output of the whole tract. Results will be presented from a finite element simulation of the acoustic effects of two constrictions that vary independently in location and size. The location of each constriction varied in 34 steps and the size varied in 16 steps. Independent variation of the two constrictions yields 295 936 constriction combinations. The function relating the acoustic output of the multiply constricted tract to the acoustic effects of each of the constrictions when made alone is generally nonlinear. Several features of this function will be discussed, and conditions for its linearization will also be presented. [Work supported by NIH.]