A Perceptual Study on Linearly Approximated FO Contours in Cantonese Speech

F0 variation in speech is known to carry abundant information, both linguistic and paralinguistic. Its impact on speech communication is thus widely concerned. F0 variation in speech, being a major super-segmental acoustic feature, has received a lot of attention, particularly from the perspectives of production-acoustics and perception-acoustics. However, it is noted that perception-acoustic knowledge of F0 variation in association with speech naturalness is quite limited. This is especially the case in the studies of tonal languages, in which most efforts are made on acoustic cues related to tone identification.;F0 contours measured from human speech (observed contours) generally vary to a considerable extent. This research attempts to investigate perception-critical variations in these highly varying contours. In particular, F0 contours in Cantonese speech are concerned. Cantonese is a major Chinese dialect that is known of being rich in tones. Psychoacoustic findings suggest that human perception has limitations in perceiving pitch movements. This means that not all of the variations in the observed contours are perceivable. A major problem addressed in this study is to find the simplest acoustic representation of an observed F0 contour that is adequate to attain comparable perception with the natural speech.;Approximation of F0 contours in Cantonese speech is investigated. Multiple approximations are examined and evaluated. The modified speech utterances that carry the approximated contours at syllable, word and sentence levels are perceptually examined with reference to natural speech. It is found that linear approximation can adequately describe all perception-sensitive F0 variations in Cantonese speech. Each tone contour can be represented by one or two linear movements, and the transition between co-articulated tones can be represented by one linear movement.;The feasibility of using linear approximation greatly simplifies the way to understand and interpret F0 variations in speech processing, by the means of learning the properties of linear movements. Three steps of analysis are carried out on the generated linear approximations. The first one examines the movement slopes in the approximated F0 contours of isolated syllables, in comparison with the perceptual thresholds found in the psychoacoustic studies. The second analysis is performed over a set of linearly approximated F0 contours of polysyllabic Cantonese words. The determining attributes of these linear movements, i.e., movement slopes, movement heights and time locations of turning points are analyzed statistically. The last analysis concerns the evaluation of modified F0 contours. Objective evaluations are compared with perceptual evaluation. These analyses provide knowledge which can improve our understanding on how F0 variations are processed in speech path.;To explore the potentials oflinear approximation in research of speech prosody, a perception-oriented framework of automatic approximation is developed, so as to replace the manual process in the feasibility study. The framework aims to make the process of deriving approximations standardized, consistent and efficient. It is formulated based on the experiences from manual approximations and is also implemented with other perceptual findings. The initial test on polysyllabic words gives promising results.