Qiguang Lin James Flanagan ChiWei Che
CAIP Ctr., Rutgers Univ., Piscataway, NJ 08855-1390
In this paper acoustics and synthesis of nasalization is studied based on a comprehensive computer model of the vocal tract: TRACTTALK. TRACTTALK simulates the vocal-tract system in the frequency domain and derives the time-domain equivalent to produce sound output. It incorporates all important components of the system and decomposes the transfer function into its zero and pole parts. Such a decomposition enables one to accurately estimate poles and zeros of a nasalized sound. First, temporal trajectories of poles/zeros are examined as a function of the velopharyngeal opening, the presence of the nasal sinuses, and other articulatory parameters. This is in follow-up to previous work [Flanagan, AT&T Bell Labs. internal report (1983)]. The attempt is to systematically characterize the pole/zero pattern of nasalization for improving the performance of formant tracking and feature labeling algorithms. Secondly, synthesis of nasalization is described using TRACTTALK. Listening experiments are conducted to assess the relationships among perceived nasality, inclusion of the nasal sinuses, and the degree of the velopharyngeal opening. It is found, e.g., that inclusion of the nasal sinuses results in stronger perceived nasality. While the literature reports differing views on the role of sinuses in nasality, these results are consistent with the findings of Maeda [Proc. ICASSP 2, 911--914 (1982)]. Synthetic speech generated from the vocal-tract system will be demonstrated.