Effects of speaking rate on vowel formant trajectories

Abstract

The effects of speaking rate and vowel context on formant frequencies have traditionally been assessed by analyzing the variation in some operationally defined ‘‘target’’ frequency value. The use of a single frequency value to describe the behavior of a formant has proven useful for distinguishing among vocalic nuclei and identifying ‘‘target undershoot’’ effects of speaking rate. We have, however, only limited understanding of the characteristic effects of speaking rate change on formant trajectories. In our work, analysis of more complete representations of the time-varying changes in formant frequencies throughout vocalic nuclei have revealed patterns of formant change across speaking rates that differ qualitatively and quantitatively between speakers. These data suggest speaker-specific strategies for accomplishing speaking rate change. We have also observed that the acoustic effects of rate change within speakers differ qualitatively and quantitatively between different ranges of the vowel duration continuum. Thus, the acoustic effects of small changes in speaking rate at speaking rate extremes are not comparable to quantitatively identical changes at habitual rates. Since changes in speaking rate are commonly thought to correspond with changes in the overlap of neighboring articulatory gestures, these findings are pertinent to modeling coarticulation. [Work supported by NIH DC 0149-10.]