Methods and studies of laryngeal voice quality analysis in speech production

Voice quality, defined by John Laver as the characteristic auditory colouring of a speaker's voice, is a significant feature of speech, and it is used to signal various properties such as emotions, intentions, and mood of the speaker. While voice quality measurement techniques and algorithms have been developed, much work is needed to obtain a comprehensive view of the function and analysis of human voice in the production of different voice qualities. Two major research questions are presented in this thesis: First, how can the most important laryngeal voice quality features be analyzed, and second, how do the voice quality features affect different facets of vocal expression? To answer these questions, five separate studies of the analysis methodology and two studies regarding the voice quality behaviour were published. The methodology articles describe a voice source analysis software package; a comparison of multiple voice source parameters in breathy, normal, and pressed phonation; a method for evaluating inverse filtering algorithms; comparison of two inverse filtering algorithms; and a method for analyzing intensity regulation of speech. One analysis article studies changes in the laryngeal voice quality when different emotions are expressed in speech and another voice quality changes in expression of prominence in continuous speech. The methodology studies resulted in new tools, methods, and guidelines for voice source analysis, while the analysis studies provide information on how voice quality is used in expressive speech