The surface wave model of phonation threshold pressure and physical models of the vocal fold mucosa: Theory and experiment.

Abstract

One of the simpler manifestations of the role of the vertical phase difference in transferring energy from the glottal airflow to the motion of the vocal folds is the surface wave model (SWM) developed by Titze in 1988. He predicted that the phonation threshold pressure (PTP) should decrease as the glottal half width decreases and as the vocal fold thickness increases, and increase as the tissue damping increases, if no vocal tract is present. Further, his treatment of the SWM predicts that for a given glottal half width, converging glottal shapes should have a higher PTP than diverging glottal shapes. Although some of the experiments done with physical models of the vocal fold mucosa support these predictions, the measurements of the angle dependence of the PTP [Chan et al., “Further studies of phonation threshold pressure in a physical model of the vocal fold mucosa,” J. Acoust. Soc. Am. 101, 3722–3727 (1997)] do not follow the expected trend. A recent re-examination of the SWM found that the diverging-converging question is sensitive to the value of the entrance loss coefficient. Values of the coefficient near 1.37 seem to remove the discrepancy with the data. [Work supported by NIH R01DC03577.]