An ultimate goal of speech research is to develop a common theoretical framework that will link together vocal fold dynamics, aerodynamics, acoustics, and speech perception. Such a unified approach is essential in explaining how tissue movement finally results in the perception of speech sounds. Because of its role both as a coupled oscillator with the vocal folds and as the acoustic source, the glottal airflow provides information about both vocal fold vibration and the resulting acoustic signal that listeners ultimately perceive as voice quality. While the field of aeroacoustics and the theory of vortex sound are relatively advanced, the application of such theories to voice production is still in its infancy. Accordingly, exploitation of such theories in a comprehensive, systematic study of phonation over a broad range of phonatory conditions holds considerable promise for furthering our understanding of voice source mechanisms. Over a five-year period, we propose to address the following Specific Aims using analytic/computational models of phonation and three laboratory models of phonation (a driven physical model, a self-oscillating physical model, and human excised larynges): (1) quantify the near field glottal airflow over the breathy to pressed voice continuum, as manipulated by glottal adduction, (2) quantify the near field glottal airflow as a function of voice type (chest, falsetto, vocal fry), as induced by changes in the body/cover parameters of the vocal folds, (3) quantify the near field glottal airflow as a function of source/tract interactions, (4) quantify the near field glottal airflow as a function of left-right asymmetries of the vocal folds. For each of these Specific Aims, we will measure the near field glottal airflow, identify the voice source mechanisms contained therein, quantify the relative contribution of these voice source terms to the radiated acoustic output, and perform a spatio-temporal decomposition of the near field glottal airflow to extract the primary orthogonal models of the airflow and reveal the interaction of these modes in this critical sound-producing region.
Successful completion of the proposed research will not only improve our understanding of voice source mechanisms across a variety of normal and disordered voice types, but also reveal relationships and interactions between various elements of the speech chain including vocal fold dynamics, aerodynamics, acoustics, and perception. In the future, this knowledge eventually may be conceptualized in the development of accurate, efficient, reduced-order models of phonation which may assist in practical clinical applications.
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