A voice source taking account of coupling with the supraglottal cavities

A glottal source model generating a volume velocity signal and including the interaction with the vocal cavities is discussed. The model is loaded by an equivalent circuit for the driving point impedance of the vocal tract. This circuit is controlled dynamically by the first two formant frequencies. The synthesis of this circuit is based on the results we have obtained from a simulation of a lossy vocal tract transmission-line model. A "coupling index" is defined as a measure of the degree of tract-source interaction which is found to be important for all the first formant range. The effects of this interaction on the shape and spectrum of the volume velocity wave is demonstrated. Among other phenomena observed on human speech, the increase of the first formant amplitude with increasing F0, at a higher rate than that predicted when no interaction is assumed, can be explained by the coupling effects. A simulation on a digital computer of this model was achieved and an analog construction is being investigated and will be used for perception tests.