Performance evaluation of glottal quality measures from the perspective of vocal tract filter consistency

The main difficulty in glottal waveform estimation is the separation of the unknown vocal tract and glottal components of the speech signal. Several glottal quality measures (GQM’s) have been proposed to objectively assess the quality of source-tract separation by exploiting known properties of glottal waveforms. In this paper, we present a performance evaluation of 10 GQM’s based on the consistency of estimated vocal tract filters (VTF’s) on sustained vowel utterances. We compare the results obtained using GQM’s to select the optimal estimates to the case where the linear prediction window is aligned exactly with the glottal closure instant (GCI). Although GCI use resulted in the most consistent VTF’s, there was a significant benefit from combining several GQM’s for selecting optimal estimates. In addition, the GQM-derived estimates were shown to have higher divergence than the GCI estimates across some phoneme-pairs, suggesting higher class-separability.