A robust method for determining instants of major excitations in voiced speech

We propose a method for determining the instants of significant excitation in speech signals using the negative derivative of the unwrapped phase (group delay) function of the short time Fourier transform. Here significant excitation refers primarily to the instants of glottal closure in voiced speech. The method computes the average slope of the unwrapped phase spectrum as a function of time. The instants where the phase slope function makes a positive zero-crossing correspond to the major excitations in the signal. For an analysis window size in the range of one to two pitch periods, these instants coincide with the instants of glottal closure in each pitch period. The method is robust, as it depends only on the average phase slope value, and further, it depends only on the positive zero-crossing instants of the average phase slope function.