Some techniques for controlling distinctive contours of speech parameters in experimental manipulation
David Graff, Franz Seitz · The Journal of the Acoustical Society of America · 1984
All acoustical properties which contribute to signaling phonemic contrasts are, to some extent, “time-varying.” However, some properties, e.g., formant trajectories in diphthongs and fundamental frequency trajectories in tones, rely for their distinctiveness on time-varying contours which are quite complex. These complex contours are composites of two or more parameters, e.g., duration, rate of change, and relative values of extrema. Experiments concerned with the contribution of particular aspects of the contours' patterns to the perception of phoneme categories face the following problem: How are such composites of parameters to be controlled and modified to produce a synthetic continuum of variants for the basic ceteris paribus experimental paradigm? This report presents some techniques that we have devised which address this problem, and evaluates their effectiveness in LPC and terminal analog synthesis. The contours of formant trajectories in varieties of English, and the contours of fundamental frequency trajectories in Vietnamese tones, have been systematically modified using these techniques in order to produce stimulus sets. The central problems were time-warping and interpolating smooth curves through data points.