Speaking rate effects on formants

By J. Berry and G. Weismer

Formant data have conventionally been extracted from a single point in time within a vocalic nucleus. Speaking rate effects on these discrete formant measures appear to be complex and idiosyncratic (Tjaden & Weismer, 1998). Formant “trajectories” reflect time-varying changes in vocal tract configuration (Stevens, 1998), and are sensitive to the speech production deficit in motor speech disorders (Weismer et al, 1988, 1992; Weismer, Tjaden & Kent, 1995). Yet, there are few data on trajectory characteristics. In this study, speaking rate effects on discrete formant values and formant trajectories are explored. Data are analyzed from six speakers producing 160 repetitions of “bead”, “bag”, and “boy”, embedded in a carrier phrase, across a wide, and nearly continuous range of speaking rates. Results provide further evidence that discrete spectral measures may be insufficient for adequately characterizing speaking rate effects for different speakers and vowels. Speaker-specific strategies for rate change may be evidenced by individual tendencies toward trajectory “shape-shifting.” Also, the relationships between speaking rate and spectral measures appear to be distinct between different ranges of the speaking rate continuum. Findings will be discussed with respect to the development of a model of the rate disorder associated with certain types of dysarthria.