Voice quality depends mainly on the voice source. A theoretical investigation of glottal flow models was conducted and the correspondance between time-domain models and analytic spectra has been worked out for the main glottal flow models. With the help of this correspondance, new algorithms for the open quotient estimation were developed. We compared spectral estimation of the open quotient with electroglottographic signals. Voice source analysis using acoustic and physiological signals is also being studied.
Vocal effort is an important source of variability in speech.
Variations in fundamental frequency, duration, and glottal waveform parameters have been studied for various levels of vocal effort. A bibliography on time-frequency methods for speech signal analysis continues to be maintained and extended. Linguistic procedures for French TTS were studied in-depth as part of the doctoral thesis of Ph. Boula de Mare il, defended in December 1997. The conversion rules have been improved, particularly for difficult cases, such as acronyms, proper names and abbreviations.