On the acoustic correlates of high and low nuclear pitch accents in American English

Earlier findings in Shue et al., 2007 and Shue et al., 2008 raised questions about the alignment of nuclear pitch accents in American English, which are addressed here by eliciting both high and low pitch accents in two different target words in several different positions in a single-phrase utterance (early, late but not final, and final) from 20 speakers (10 male, 10 female). Results show that the F0 peak associated with a high nuclear pitch accent is systematically displaced to an earlier point in the target word if that word is final in the phrase and thus bears the boundary-related tones as well. This effect of tonal crowding holds across speakers, genders and target words, but was not observed for low accents, adding to the growing evidence that low targets behave differently from highs. Analysis of energy shows that, across target words and genders, the average energy level of a target word is greatest at the start of an utterance and decreases with increasing proximity to the utterance boundary. Duration measures confirms the findings of existing literature on main-stress-syllable lengthening, final syllable lengthening, and lengthening associated with pitch accents, and reveals that final syllable lengthening is further enhanced if the final word also carries a pitch accent. Individual speaker analyses found that while most speakers conformed to the general trends for pitch movements there were 2/10 male and 1/10 female speakers who did not. These results show the importance of taking into account prosodic contexts and speaker variability when interpreting correlates to prosodic events such as pitch accents.