Fundamental frequency of phonation and perceived emotional stress

Nonlinguistic information about the speaker's emotional state is conveyed in spoken utterances by means of several acoustic characteristics and listeners can often reliably identify such information. In this study we investigated the effect of short- and long-term F0 measures on perceived emotional stress using stimuli synthesized with the LPC coefficients of a steady vowel and varying F0 tracks. The original F0 tracks were taken from naturally occurring speech in highly stressful (contingent on terror) and nonstressful conditions. Stimuli with more jitter were rated as sounding more hoarse but not more stressed, i.e., a demonstrably perceptible amount of jitter did not seem to play a role in perceived emotional stress. Reversing the temporal pattern of F0 did not affect the stress ratings, suggesting that the directionality of variations in F0 does not convey emotional stress information. Mean and maximum F0 within an utterance correlated highly with stress ratings, but the range of F0 did not correlate significantly with the stress ratings, especially after the effect of maximum F0 was removed in stepwise regression. It is concluded that the range of F0 per se does not contribute to the perception of emotional stress, whereas maximum F0 constitutes the primary indicator. The observed effects held across several voices that were found to sound natural (three male voices and one of two female ones). An effect of the formant frequencies was also observed in the stimuli with the lowest F0; it is hypothesized that formant frequency structure dominated the F0 effect in the one voice that gave discrepant results.