Asymmetric kinematic changes in speaking rate explored with FDA

Abstract

We report preliminary results for the effect on tongue movements of varying speaking rate. Speech acoustics and tongue tip and body kinematic data were collected using electromagnetic articulography (EMA) [Perkell et al., J. Acoust. Soc. Am. 92 (1992)]. A subject read each one of 20 sentences three times in a row with a predefined order of combination of three speaking rates (normal, medium, fast). Velocity and acceleration were derived using functional data analysis (FDA) [Ramsay et al., J. Acoust. Soc. Am. 99 (1996)] for smoother estimation of acceleration from the displacement data. Global utterance analyses of phase-space and variability in the displacement-velocity and the velocity-acceleration relations indicate that the fast speech exhibits comparable tongue tip displacements to normal speech but significantly larger accelerations (p<0.00). The difference in the order of combination of speaking rates (e.g., normal changing to fast versus fast to normal) shows significant effects on both voicing effort (expressed as rms energy) and the kinematic parameters. Finally, kinematic variability at some points in the utterance is much more constrained than at other points, irrespective of speaking rate. A possible interpretation of this is that particular portions of the utterance require this stability for linguistic or articulatory reasons. [Work supported by NIH.]