Effect of speaking rate and contrastive stress on formant dynamics and vowel perception

Abstract

Vowel formants play an important role in speech theories and applications; however, the same formant values measured for the steady-state part of a vowel can correspond to different vowel categories. Experimental evidence indicates that dynamic information can also contribute to vowel characterization. Hence, dynamically modeling formant transitions may lead to quantitatively testable predictions in vowel categorization. Because the articulatory strategy used to manage different speaking rates and contrastive stress may depend on speaker and situation, the parameter values of a dynamic formant model may vary with speaking rate and stress. In most experiments speaking rate is rarely controlled, only two or three rates are tested, and most corpora contain just a few repetitions of each item. As a consequence, the dependence of dynamic models on those factors is difficult to gauge. This article presents a study of 2300 [iai] or [i epsilon i] stimuli produced by two speakers at nine or ten speaking rates in a carrier sentence for two contrastive stress patterns. The corpus was perceptually evaluated by naive listeners. Formant frequencies were measured during the steady-state parts of the stimuli, and the formant transitions were dynamically and kinematically modeled. The results indicate that (1) the corpus was characterized by a contextual assimilation instead of a centralization effect; (2) dynamic or kinematic modeling was equivalent as far as the analysis of the model parameters was concerned; (3) the dependence of the model parameter estimates on speaking rate and stress suggests that the formant transitions were sharper for high speaking rate, but no consistent trend was found for contrastive stress; (4) the formant frequencies measured in the steady-state parts of the vowels were sufficient to explain the perceptual results while the dynamic parameters of the models were not.

Effects of prosodic factors on spectral dynamics. I. Analysis

“…Furui ͑1986͒, in a series of experiments, showed that speech segments of 10 ms, excised at the point of maximum spectral change, contain the most important information for identification of consonant-vowel transitions. In spite of the perceptual importance of vowel dynamics, Watson andHarrington ͑1999͒ andPitermann ͑2000͒ reported no improvements in automatic vowel classification when dynamic parameters were added to static features. Watson and Harrington ͑1999͒ argued that dynamic information, such as spectral rate of change, may be related to prosodic aspects of vowels rather than carrying phonetic information.…”

Speaking Rate Effects on Normal Aspects of Articulation: Outcomes and Issues

“…Despite the preceding discussion, which suggests that acoustic effects of rate change may be small (relative to kinematic variability), studies of the acoustic effects of speaking rate change have identified a variety of speaker and context-related effects on formants (Agwuele, Sussman, & Lindblom, 2008;Fourakis, 1991;Gay, 1968Gay, , 1978Hertrich & Ackermann, 1995;Lindblom, 1963;Pitermann, 2000;Rosen et al, 2011;Tjaden & Weismer, 1998;van Son & Pols, 1992;Weismer & Berry, 2003). Taken together, these studies indicate a wide range of possible speaker-specific and context-related effects of speaking rate change.…”

Filling the perceptuo-motor gap

“…Indeed, if reduction is too strong, the recovery may fail (see e.g. Pitermann, 2000). Moreover, if recovery were complete, automatic and effortless, there would be no need (1) The listener is able to process current height and duration in order to separately recover the intended height control (vowel reduction) 1 and the intended vowel duration; (2) Recovery is constrained by both articulatory knowledge and auditory processing, as shown by the organization of sound systems in human languages.…”

“…Indeed, if reduction is too strong, the recovery may fail (see e.g. Pitermann, 2000). Moreover, if recovery were complete, automatic and effortless, there would be no need for a speaker to hyperarticulate, while the control of articulatory strength is obviously part of the speaker's program (see Moon & Lindblom, 1994).…”