Experimental study of the target undershoot model using acoustic and ‘‘articulatory’’ data

Abstract

In a previous study [M. Pitermann and J. Schoentgen, 1st ESCA Tutorial and Research Workshop on Speech Production Modeling, 17–20 (1996)], the influence of speaking rate and emphatic stress on formant frequencies and corresponding target estimates were analyzed for the vowels [a] and [ε] in an [i-i] context. Unreached targets were estimated by means of two dynamic and two kinetic models of formant transitions. The results showed that both formant frequencies and target estimates varied with speaking rate and emphatic stress. In the present survey, we analyzed ‘‘articulatory’’ targets for the same corpus in the framework of a vocal tract model. The ‘‘articulatory’’ trajectories were analytically calculated by means of an acoustic-to-articulatory inversion carried out on a six-tube Kelly-Lochbaum model of the vocal tract [S. Ciocea, ‘‘Semi-analytic formant-to-area mapping,’’ Ph.D. thesis (1997)]. Targets were then estimated by means of asymptotes or steady-state solutions of transition models fitted to trajectories of the palatal region. The results suggest that ‘‘articulatory’’ target estimates did not depend on speaking rate, emphatic stress and speaker for a subset of speaking rate and stress pairs. The results will be discussed with respect to possible inversion artifacts and the possibility of target invariance.