Estimation of glottal closure instants from telephone speech using a group delay-based approach that considers speech signal as a spectrum

Glottal closure instants (GCIs) are characterized by a strong negative valley in the speech signal and an abrupt change in the amplitude. In this paper, an algorithm that exploits these two properties of a GCI is proposed to estimate the location of GCIs, specifically from telephone speech. The algorithm considers a symmetrized voiced segment as the Fourier transform of an even signal. In such a case, the negative valleys in the spectrum correspond to zeros that lie outside the unit circle in the z-plane. The angular location of these zeros indicate the location of the GCIs. The angular location can be estimated from the group delay spectrum of the even signal, since a phase change of 2π, between adjacent frequency bins, occurs at the location of a zero that lies outside the unit circle. The performance of the algorithm is evaluated on a simulated speech corpora derived from CMU and CSTR databases and the NTIMIT database, in terms of identification, false alarm, and miss rates. The proposed algorithm is compared with DYPSA, YAGA, and SEDREAMS, and is found to outperform all the algorithms when used on telephone speech.