Significance of Radius in the Phase-Difference-Based Approach to the Estimation of Glottal Closure Instants

The phase-difference (PD)-based approach to the estimation of glottal closure instants (GCIs), basically considers the given speech signal to be the Fourier Transform (FT) of an arbitrary even signal, such that the valleys corresponding to GCIs in the signal would now correspond to zeros lying outside the unit circle. The angular locations of these zeros can be easily identified from the phase-difference (PD) spectrum, which has a value of 27 at these locations. However, measuring the FT on the unit circle, as is conventionally done, would result in spurious spikes in the PD spectrum, thereby increasing the ambiguity with which GCIs can be detected. In order to circumvent this, the FT could be measured outside the unit circle, that is, at a radius greater than one. This radius has to be chosen carefully, since measuring the FT at too high a radius would result in missing GCIs and too low a radius would result in spurious GCIs. Therefore, the current work focuses on analyzing the significance of the radius in the accurate estimation of GCIs and on automatically identifying the most suitable radius, at which the PD spectrum could be derived, based on the characteristics of a given speech signal.