The characteristics of a static and dynamic model of the vocal source
A. Al-Ansari, P. Badin, Bernard Guérin · The Journal of the Acoustical Society of America · 1981
We use a computer two-mass model of the human vocal cords to study the acoustic behavior of the vocal source. This model is directly controlled by two parameters: The subglottal pressure Ps and the cord mass-tension coefficient Q. The glottal signal issued from the model can be characterized by its fundamental frequency F0, the opening ratio QO, and the dissymmetry ration (or speed quotient) QD. The result of the static model simulation is in accordance with the previously obtained characteristics of the glottal signal [B. Guerin and L. J. Boe, Phonetica 37-3, 169–192 (1980) and J. L. Flanagan, K. Ishazaka, and R. L. Shipley Bell Syst. Tech. J. 54, 485–506 (1975)]. It indicates that the principal features of human vocal cord behavior are well presented by the static model. In order to see how the dynamic aspect can affect the static properties, we inject different slope pulses representing either the lung pressure or the cord mass-tension parameters in the two-mass model. These pulses are equivalent to that, induced by pushing on the chest or generated by laryngeal muscle activities of a phonating subject. We show that the variations of F0 and QO with P8 or Q depend on the sign and the value of the pulse slope. Their evolutions are separated from the static curves in an almost regular way, QD variations depend only on pulse slope value and scatter plot results for QD versus P8 or Q.