Analysis of singing voice for epoch extraction using Zero Frequency Filtering method

Epoch is the instant of significant excitation of the vocal tract system during the production of voiced speech. Estimation of epochs or Glottal closure instants (GCIs) is a well studied topic in the speech analysis. From the recent studies on GCI detection from singing voice with state-of-art methods proposed for speech, there exist a clear gap in accuracy between speech and singing voice. This is because of source-filter interaction in singing voice compared to speech. Performance of existing algorithms deteriorates as most of the techniques depends on the ability to model the vocal tract system in order to emphasize the excitation characteristics in the residual. The objective of this paper is to analyze the singing voice for the estimation of epochs by studying the characteristics of the source-filter interaction and the effect of wider range of pitch using the Zero Frequency Filtering (ZFF) method. It is observed that high source-filter interaction can be captured in the form of the impulse-like excitation by passing the signal through three ideal digital resonators having poles at zero frequency, and the effect of wider range of pitch can be controlled by processing short segment (0.4-0.5 sec) signal.