Analysis of Glottal Stop in Assam Sora Language

The objective of this work is to characterize the intervocalic glottal stops in Assam Sora. Assam Sora is a low resource language of the South Munda language family. Glottal stops are produced with gestures in the deep laryngeal level; hence, the estimated excitation source signal is used in this study to characterize the source dynamics during the production of Assam Sora glottal stops. From that, temporal domain voice source features, Quasi-Open Quotient (QOQ) and Normalized Amplitude Quotient (NAQ) are extracted along with spectral features such as H1-H2 ratio and Harmonic Richness Factor (HRF). One excitation source feature is extracted from the zero frequency filtered version of the speech signal to characterize the variations within the glottal cycles in glottal stop region. A recently proposed wavelet based voice source feature, Maxima Dispersion Quotient (MDQ) is also used to characterize the abrupt glottal closure during glottal stop production. From the analysis, it is observed that the features are salient enough to uniquely characterize glottal stops from the adjacent vowel sounds and may also be used in continuous speech. A Mann-Whitney U test confirmed the statistical significance of the differences between glottal stops and their adjacent vowels.