The influence of speech rate on Fujisaki model parameters

Abstract

The current paper examines influences of speech rate on Fujisaki model parameters based on read speech from the BonnTempo-Corpus containing productions by 12 native speakers of German at five different intended tempo levels (very slow, slow, normal, fast, fastest possible). The normal condition was produced at an average rate of 6.34 syllables/s or 100%, the very slow version at 67%, and the fastest version at 161% of the normal rate. We extracted F0 contours and subjected them to decomposition using the Fujisaki model. We ordered all the data with respect to their actual speech rates. First, we assessed how prosodic realizations vary with speech rate and examined phrase command magnitudes, the number of phrase commands as well as the base frequency, accent command amplitudes, and the timing of accent command with respects to the underlying syllables and their nuclear vowels. Second, we analyzed between-sentence variability within and between speakers and investigated whether and how the prosodic structure is preserved at different speech rates. For very slow speech, we found for some of the speakers that the original phrase structure had disintegrated into something like a list of isolated words separated by pauses. Very fast speech became chains of uniform syllables at very high pitch and with almost flat intonation. With respect to the F0 range reflected by the amplitude of accent commands, we found strong interspeaker differences. While four of the subjects exhibited a significant reduction at higher speech rates, the others did not. As speed increases, it appears that F0 gestures commence earlier in the syllable, that is, the onset time of accent commands is located closer to the syllable/vowel onset than at lower speed.