Page de résumé pour/Title page for FPMSetd-10272005-095325


Type de document Thèse/Dissertation
Auteur Bozkurt, Baris
Adresse e-mail de l'auteur Baris.Bozkurt@fpms.ac.be
URN FPMSetd-10272005-095325
Langue Anglais/English
Titre Zeros of the z-transform (ZZT) representation and chirp group delay processing for the analysis of source and filter characteristics of speech signals
Intitulé du diplôme DOCSCAPPL - Doctorat en Sciences appliquées
Département ELEC - département électricité
Adresse e-mail du département
Jury
Nom Titre
D'Alessandro, Christophe Membre du jury/Committee Member
Doval, Boris Membre du jury/Committee Member
Lybaert, Paul Membre du jury/Committee Member
Pagel, Vincent Membre du jury/Committee Member
Pirlot, Marc Président du jury/Committee Chair
Dutoit, Thierry Promoteur/Director
Mots-clés
  • group delay processing
  • phase processing
  • zeros of z-transforms
  • formant tracking
  • global flow estimation
  • source-filter separation
  • spectral representation
Date de défense 2005-10-27
Type d'accès unrestricted
Résumé
This study proposes a new spectral representation called the Zeros of Z-Transform (ZZT), which is an all-zero representation of the z-transform of the signal. In addition, new chirp group delay processing techniques are developed for analysis of resonances of a signal. The combination of the ZZT representation with the chirp group delay processing algorithms provides a useful domain to study resonance characteristics of source and filter components of speech. Using the two representations, effective algorithms are developed for: source-tract decomposition of speech, glottal flow parameter estimation, formant tracking and feature extraction for speech recognition.

The ZZT representation is mainly important for theoretical studies. Studying the ZZT of a signal is essential to be able to develop effective chirp group delay processing methods. Therefore, first the ZZT representation of the source-filter model of speech is studied for providing a theoretical background. We confirm through ZZT representation that anti-causality of the glottal flow signal introduces mixed-phase characteristics in speech signals. The ZZT of windowed speech signals is also studied since windowing cannot be avoided in practical signal processing algorithms and the effect of windowing on ZZT representation is drastic. We show that separate patterns exist in ZZT representations of windowed speech signals for the glottal flow and the vocal tract contributions. A decomposition method for source-tract separation is developed based on these patterns in ZZT.

We define chirp group delay as group delay calculated on a circle other than the unit circle in z-plane. The need to compute group delay on a circle other than the unit circle comes from the fact that group delay spectra are often very noisy and cannot be easily processed for formant tracking purposes (the reasons are explained through ZZT representation). In this thesis, we propose methods to avoid such problems by modifying the ZZT of a signal and further computing the chirp group delay spectrum. New algorithms based on processing of the chirp group delay spectrum are developed for formant tracking and feature estimation for speech recognition. The proposed algorithms are compared to state-of-the-art techniques. Equivalent or higher efficiency is obtained for all proposed algorithms.

The theoretical parts of the thesis further discuss a mixed-phase model for speech and phase processing problems in detail.

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