The contribution of intonation, segmental durations, and spectral features to the perception of a spontaneous and a read speaking style

The influence of pitch contour, segmental durations, and spectral features on the perception of two speaking styles was studied. For this purpose two male speakers each spoke “spontaneously” to an interviewer and afterwards read out their own literally transcribed spontaneous text. Pairs of identical spontaneous and read utterances were selected that were fluently spoken in both speaking styles (no false starts, hesitations, etc.). Five test conditions were constructed in which the utterances had: (1) no manipulations; (2) phoneme durations from the opposite speaking style; (3) the pitch contour from the opposite speaking style; (4) a monotonous pitch contour; (5) the original spectral features combined with the prosodic features of the opposite speaking style. The stimuli were presented to 32 subjects in a listening experiment. Their task was to classify each utterance as either “spontaneous” or “read out” speech. All manipulations of the test utterances had a significant effect on the classification of the speaking style. We also analysed the original utterances with respect to several acoustic measures for intonation, duration, jitter and shimmer, and spectral vowel quality. Overall, read speech compared to spontaneous speech had: a lower articulation rate, more F,, variation, more F,, declination, less shimmer, and less vowel reduction. However, none of these acoustic features by itself can clearly discriminate between the two speaking styles. Above all it became clear that the performance of the speakers and the listeners varied enormously.