The effect of speaking rate on consonant vowel coarticulation

In 2007 Lindblom et al. introduced a methodological tool to disentangle consonant-vowel (CV) coarticulation attributable to emphatic stress apart from the vowel expansion effects known to accompany the prosodic overlay. After empirically accounting for the altered vowel positions, they reported small but consistent increases in F2 transition onsets in emphatically produced CVs that could not be attributed to vowel context influences, and that differed across stop place. At issue is whether the findings of these authors can be replicated, but in the opposite direction, for CVs produced at fast speaking rates. A modified locus equation regression metric was similarly used to account for rate-induced vowel reduction effects in predicting frequencies of F2 transition onsets in rapid speech. Six American-English speakers produced [V1.CV2] sequences embedded in a carrier sentence, at three speaking tempos: normal, fast, and fastest. Significant differences were found between 'predicted' and 'observed' F2 onsets across stops, with alveolars and velars showing greater decreases in F2 onsets during more rapid speech than labials. The complementary findings are discussed relative to a unified view of anticipatory coarticulation in CV production across a continuum of hyperarticulated spectral expansion to hypoarticulated spectral reduction.