| Abstract |
Voice quality is a complex attribute of voice but one important aspect arises from the regularity and duration of the closed phase from vocal fold cycle to cycle. The determination of closed phase requires tha accurate detection of glottal closure (GCI) and glottal opening (GOI) instant. In literature, many methods have been suggested on this direction employing either the Electoglottographic (EGG) or the speech signal. This work presents a robust algorithm for the detection of glottal instants from the EGG signal and a study on the interaction between Amplitude-Frequency components of speech and glottal phases.
The determination of GCIs and GOIs, is quite straightforward using Electroglottographic (EEG) signals, The derivative of EGG offers a simple way in detecting the important instances during the production of speech; the glottal closing and opening instants. In this thesis we suggest an alternative method to the simple derivative which is based on the spectral methods. Spectral methods provide an elegant way to conduct first and higher order derivatives on discrete time data, with high accuracy.
Furthermore, we introduce a new way to differentiate the EGG signal for estimating the main glottal instants. The gradient of electoglottogrpahic signal is performed with a method referred to as "Slope Filtering". This approach shows to be robust in revealing the major peaks in the slope filtered EGG signal, even in cases where the quality of the EGG recordings is not good. Contrary to the simple derivative of the EGG signal, the peaks can be well distinguished and uniquely specified in the slope filtered signal. The proposed method exhibits high accuracy of voiced segments, including the onset and offset regions.
The derivation of glottal phases from speech signal has drawn great attention in recent years. A novel approach, relying on the speech signal, is proposed nased on a Quasi-Harmonic (QHM) representation of speech. The adaptive QHM algorithm estimates the instantaneous AM-FM components of the speech signal. The extracted components, which are used for the reconstruction of the signal, are correlated to the glottal phases generated from the EGG signal. The AM component follows a steady pattern for each glottal phasem whereas the FM component shows low variations for various speakers.
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Determining glottal closure and opening instants in speech
