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Francis GRENEZ


coordonnées


Ecole polytechnique de Bruxelles
Francis GRENEZ
tel 02 650 30 92, fax 02 650 47 13, Grenez.Francis@ulb.ac.be
Campus du Solbosch
CP165/51, avenue F.D. Roosevelt 50, 1050 Bruxelles



unités de recherche


Traitement des Signaux (LIST/TS) [Signal Processing Group] (LIST/TS)



projets


ECLIPSE - Functional assessment of disordered voices and real-time monitoring under field conditions - Evaluation fonctionnelle clinique des pathologies vocales et suive embarqué [ECLIPSE - Functional assessment of disordered voices and real-time monitoring under field conditions]
The objective is the development of novel speech analysis methods that enable describing normal and pathological voices reliably and validly on the base of connected speech (as opposed to sustained vowels, which are the norm). High-speed imaging of the vibrating vocal folds is combined with acoustic analysis of sustained sounds to provide for clinical use multiple modalities that complement each other. The overall objective is the development of a clinical workstation running multiple analysis algorithms and the building of a portable device that enables monitoring speakers under field conditions. This project is a common project with the University of Mons and the Catholic University of Louvain. Cette recherche consiste à développer des nouvelles méthodes d'analyse du signal de parole permettant de caractériser de manière objective les voix pathologiques. Les techniques sont applicables à la parole continue contrairement aux méthodes actuelles qui sont limitées à l'analyse des voyelles soutenues. En parallèle, un traitement d'images des cordes vocales, prises par caméra haute vitesse, est mis à profit pour mettre en place une analyse multimodale et d'en d'améliorer l'efficacité. L'objectif global du projet est de développer une station de travail clinique incluant les logiciels d'analyse dédiés ainsi que la réalisation d'un dispositif portable permettant un suivi en continu des locuteurs à risque. Ce projet est réalisé en collaboration avec l'Université de Mons et l'Université Catholique de Louvain. [The objective is the development of novel speech analysis methods that enable describing normal and pathological voices reliably and validly on the base of connected speech (as opposed to sustained vowels, which are the norm). High-speed imaging of the vibrating vocal folds is combined with acoustic analysis of sustained sounds to provide for clinical use multiple modalities that complement each other. The overall objective is the development of a clinical workstation running multiple analysis algorithms and the building of a portable device that enables monitoring speakers under field conditions. This project is a common project with the University of Mons and the Catholic University of Louvain.]

Analysis of vocal tremor - Analyse du tremblement vocal [Analysis of vocal tremor]
The objective of the project is to analyse and describe vocal tremor in normophonic and dysphonic subjects. Vocal tremor is a modulation of the vocal frequency in an interval from 1 to 15 Hz. The estimation of the tremor frequency and depth is based on an algorithm that obtains the instants of glottal closure from the speech signal without an a priori knowledge of the average vocal frequency. Speech tremor owing to tremor of the articulators is estimated via the speech formants. The analysis is applied to normal subjects and speakers suffereing from Parkinson's disease, amyotrophic lateral sclerosis and vocal fatigue. Au cours de ce projet, nous étudions et quantifions les différentes composantes du tremblement vocal, à la fois chez des sujets normophoniques et dysphoniques. Pour étudier le tremblement dû à la source vocale, on développe un algorithme de mesure des caractéristiques du bruit de modulation en fréquence du signal de parole. Pour étudier le tremblement dû au conduit vocal, on développe des algorithmes de mesure de la fréquence des formants et des caractéristiques de variation de ceux-ci. Ces méthodes sont testées sur des signaux synthétiques, ainsi que sur des signaux réels, de sujets normaux et pathologiques. [The objective of the project is to analyse and describe vocal tremor in normophonic and dysphonic subjects. Vocal tremor is a modulation of the vocal frequency in an interval from 1 to 15 Hz. The estimation of the tremor frequency and depth is based on an algorithm that obtains the instants of glottal closure from the speech signal without an a priori knowledge of the average vocal frequency. Speech tremor owing to tremor of the articulators is estimated via the speech formants. The analysis is applied to normal subjects and speakers suffereing from Parkinson's disease, amyotrophic lateral sclerosis and vocal fatigue. ]

Synthesis of disordered voices - Synthèse des troubles de la voix [Synthesis of disordered voices]
The objective is the development of a synthesiser that simulates disordered voices. The synthesiser comprises a nonlinear model of the evolving glottal area, an aerodynamic model of the glottis and models of the wave propagation in the vocal tract and trachea. The simulated disorders are vocal jitter and shimmer, vocal frequency and amplitude tremor, diplophonia, biphonation, random cycles, additive noise owing to turbulence as well as asthenia and strain. Medical applications of the synthesis of voice disorders are the discovery of the acoustic cues of disordered voice timbres, the training of speech therapy students in the rating of disordered voices and the testing as well as calibration of acoustic analysis methods for the functional assessment of voice. L'objectif du travail est le développement d'un synthétiseur vocal en vue de la simulation des troubles de la voix. Le synthétiseur comporte un modèle numérique de la source vocale et du conduit vocal. Les perturbations simulées sont les microperturbations de cycle-à-cycle des durées et amplitudes des cycles vocaux de parole, ainsi que le tremblement vocal. D'autre types de troubles simulés sont la diplophonie, la bi-phonation et les irrégularités des cycles vocaux dues aux vibrations aléatoires des plis vocaux, ainsi que le souffle et l'asthénie ou le forçage. Les applications médicales de la synthèse vocale sont les expériences perceptuelles cliniques, la formation des cliniciens débutant, le calibrage des algorithmes d'analyses des dispériodicités vocales ainsi que la synthèse des points d'ancrage perceptifs pour les jurys d'écoute. [The objective is the development of a synthesiser that simulates disordered voices. The synthesiser comprises a nonlinear model of the evolving glottal area, an aerodynamic model of the glottis and models of the wave propagation in the vocal tract and trachea. The simulated disorders are vocal jitter and shimmer, vocal frequency and amplitude tremor, diplophonia, biphonation, random cycles, additive noise owing to turbulence as well as asthenia and strain. Medical applications of the synthesis of voice disorders are the discovery of the acoustic cues of disordered voice timbres, the training of speech therapy students in the rating of disordered voices and the testing as well as calibration of acoustic analysis methods for the functional assessment of voice. ]

Acoustic-to-articulatory mapping - Inversion acoustico-articulatoire [Acoustic-to-articulatory mapping]
Acoustic-to-articulatory mapping is the inference from the speech signal of the vocal tract shape from the glottis to the lips. A first method has consisted in recovering the vocal tract shape by means of the formant frequencies and constraints at the lips. A second method involves the inference of the vocal tract shape based on a simulation of the speech spectrum, anti-formants, sources and losses included. The objectives are the extraction of the formant frequencies by means of the inferred tract shapes as well as the representation of the speech signal in terms of morphological rather than acoustic features. L'inversion acoustico-articulatoire consiste à retrouver la forme du conduit vocal, depuis les cordes vocales jusqu'aux lèvres, à partir du signal acoustique. Une première étude a concerné la reconstruction de la fonction d'aire du conduit à partie de la connaissance des fréquences des premiers formants, en ajoutant éventuellement une contrainte sur l'ouverture aux lèvres. Une deuxième approche est basée sur une modélisation globale du spectre incluant également l'effet des anti-formants ainsi que de la source et des pertes. Les objectifs sont l'extraction des fréquences des formants ainsi que la représentation du signal de parole en termes d'indices morphologiques plutôt qu'acoustiques. [Acoustic-to-articulatory mapping is the inference from the speech signal of the vocal tract shape from the glottis to the lips. A first method has consisted in recovering the vocal tract shape by means of the formant frequencies and constraints at the lips. A second method involves the inference of the vocal tract shape based on a simulation of the speech spectrum, anti-formants, sources and losses included. The objectives are the extraction of the formant frequencies by means of the inferred tract shapes as well as the representation of the speech signal in terms of morphological rather than acoustic features.]

Speech Signal Analysis for Voice Disorders Characterization - Analyse du signal de parole pour la caractérisation des troubles de la voix [Speech Signal Analysis for Voice Disorders Characterization]
The analysis of speech is often involved in the evaluation of voice and the discrimination between disphonic and normophonic speakers. Most of the time, acoustic features of voice disorders are obtained from sustained vowels. However, sustaining speech sounds is considered to be less informative than speaking continuously. The objective of the project therefore is to monitor the voice timbre and vocal perturbations in connected speech. Vocal disperiodicities obtained are summarised by means of vocal features that report speech properties that are clinically relevant with regard to the assessment of a speaker's voice. The description of voice disorders owing to peripheral causes are also considered. L'analyse acoustique du signal de parole est souvent utilisée dans l'évaluation et la discrimination des voix pathologiques. Les mesures acoustiques utilisées pour caractériser les troubles de la voix sont extraites de voyelles soutenues. Cependant, la représentation basée sur les voyelles soutenues n'est pas toujours valide. L'estimation de paramètres à partir de la parole connectée semble plus adéquate. L'objectif de ce projet est le développement de méthodes permettant le suivi d'un locuteur au cours de la lecture d'un texte de longue durée. L'utilisation de méthodes applicables à des signaux non stationnaires est aussi envisagée. Le bruit estimé par les différentes méthodes permet de déterminer les indices pertinents utilisés dans la caractérisation des troubles de la voix du locuteur. La caractérisation de certains troubles vocaux dus à un problème neurologique périphérique, comme les voix dysarthriques, est aussi examinée. [The analysis of speech is often involved in the evaluation of voice and the discrimination between disphonic and normophonic speakers. Most of the time, acoustic features of voice disorders are obtained from sustained vowels. However, sustaining speech sounds is considered to be less informative than speaking continuously. The objective of the project therefore is to monitor the voice timbre and vocal perturbations in connected speech. Vocal disperiodicities obtained are summarised by means of vocal features that report speech properties that are clinically relevant with regard to the assessment of a speaker's voice. The description of voice disorders owing to peripheral causes are also considered. ]

Détection et prédiction de crises d'épilepsie [On-line detection and prediction of epileptic seizures]
L'objectif de cette recherche est de modéliser à l'aide de circuits oscillants l'activité électrique neuronale et son comportement pathologique lors des crises d'épilepsie. Cela permettra de mieux comprendre le processus qui amène à la crise et de connaître les paramètres qui sont les marqueurs du changement dans la dynamique de l'EEG. Des algorithmes de détection et de prédiction seront alors développés sue base des informations issues de la modélisation. [Electroencephalography is a useful tool for physicians. It can be used for diagnostic purposes in many brain's pathologies as epilepsy, sleep troubles, etc. Epilepsy is the most current pathology in this field and concerns about 1% of the population. One of the characteristics of epilepsy is the presence of repetitive seizures. Clinically, these seizures can take different forms: from muscular moves to critical convulsions called 'Grand Mal' or tonic-clonic seizure. In EEG signals, an epileptic seizure is characterized by high-voltage and rhythmic EEG waveforms. High-voltage signals show a phenomenon of high synchronous activities of the brain or a part of it. Epilepsy can be focal (or partial) if the seizure is reduced to a part of the brain, called the focus. If the entire brain is affected, the epilepsy is said to be generalized. The automatic detection of epileptic seizure is an important purpose for specialist's diagnostic, because it could save the specialist time by pointing out the seizure periods. Furthermore, another interesting challenge in the field of EEG signal processing is the ability of predicting a seizure. It could enable in the future to avoid seizures of the patients by means of different techniques. Several linear and nonlinear features have been investigated in the literature. But at the present time, it's difficult to say if an epileptic seizure is reliably predictable. In the literature, different kinds of models have been proposed to simulate EEG signals. They use neurophysiologic mechanisms and are called 'mean-field models' because of their macroscopic approach. These models are able to represent epileptic-like EEG signals as well as normal EEG signals. They strongly suggest that epileptic activity is related with the instability or quasi-instability of the system leading to rhythmic activities. Investigating this feature of epileptic process in EEG signals could permit to better understand this process and to provide a feature for characterizing the epileptic seizure in computer-based monitoring of EEG. ]



prix


Prix biennal Bell Telephone 1989

Prix Acta Technica Belgica 1980



disciplines et mots clés déclarés


Electromagnétisme - analyse du signal Informatique médicale Ingénierie biomédicale Sciences de l'ingénieur

analyse de la parole analyse en ondelettes analyse multimodale bruit vocal conduit vocal crises d'épilepsie détection et prédiction dispositif portable inversion acoustique maladie de parkinson signal de parole signaux non stationnaires simulations numérique source vocale synthèse de la parole traitement du signal de parole traitement du signal eeg tremblement vocal troubles de la voix voix pathologiques