The perceptual evaluation of F0 excursions in speech as evidenced in liveliness estimations

In order to learn how listeners evaluate F0 excursions, a set of experiments was performed in which subjects had to estimate the liveliness of utterances. The stimuli were obtained by LPC analysis of one natural utterance that was modified by resynthesizing F0, the formant frequencies, and the time scale in order to simulate some of the natural extra- and paralinguistic variations that affect F0 and/or liveliness, namely the speaker's age, sex, articulation rate, and voice register. In each case, the extent of the F0 excursions was varied in seven steps. The results showed that, as long as the stimuli appeared to have been produced in the modal register (of men, women, and children), listeners judged F0 intervals to be equivalent if they were equal in semitones. When the voice register was shifted without adjustment in articulation, listeners appeared to judge the F0 excursions in relation to the spectral space available below F1. The liveliness ratings were found to be strongly dependent on articulation rate and to be affected by the perceived age of the speaker which, with the manipulated stimuli used here, turned out to be significantly affected by the sex of the listener.