Yves Laprie

A glottal chink model for the synthesis of voiced fricatives

This paper presents a simulation framework that enables a glottal chink model to be integrated into a time-domain continuous speech synthesizer along with self-oscillating vocal folds. The glottis is then made up of two main separated components: a self-oscillating part and a constantly open chink. This feature allows the simulation of voiced fricatives, thanks to a self-oscillating model of the vocal folds to generate the voiced source, and the glottal opening that is necessary to generate the frication noise. Numerical simulations show the accuracy of the model to simulate voiced fricative, and also phonetic assimilation, such as sonorization and devoicing. The simulation framework is also used to show that the phonatory/articulatory space for generating voiced fricatives is different according to the desired sound: for instance, the minimal glottal opening for generating frication noise is shorter for /z/ than for /3/.

Extension of the single-matrix formulation of the vocal tract

The paper presents extensions of the single-matrix formulation (Mokhtari etźal., 2008, Speech Comm. 50(3) 179 - 190) that enable self-oscillation models of vocal folds, including glottal chink, to be connected to the vocal tract. They also integrate the case of a local division of the main air path into two lateral channels, as it may occur during the production of lateral consonants. Provided extensions are detailed by a reformulation of the acoustic conditions at the glottis, and at the upstream and downstream connections of bilateral channels. The simulation framework is validated through numerical simulations. The introduction of an antiresonance in the transfer function due to the presence of asymmetric bilateral channels is confirmed by the simulations. The frequency of the antiresonance agrees with the theoretical predictions. Simulations of static vowels reveal that the behavior of the vocal folds is qualitatively similar whether they are connected to the single-matrix formulation or to the classic reflection-type line analog model. Finally, the acoustic effect of the glottal chink on the production of vowels is highlighted by the simulations: the shortening of the vibrating part of the vocal folds lowers the amplitude of the glottal flow, and therefore lowers the global acoustic level radiated at the lips. It also introduces an offset in the glottal flow waveform.

High spatiotemporal cineMRI films using compressed sensing for acquiring articulatory data

The paper presents a method to acquire articulatory data from a sequence of MRI images at a high framerate. The acquisition rate is enhanced by partially collecting data in the kt-space. The combination of compressed sensing technique, along with homodyne reconstruction, enables the missing data to be recovered. The good reconstruction is guaranteed by an appropriate design of the sampling pattern. It is based on a pseudo-random Cartesian scheme, where each line is partially acquired for use of the homodyne reconstruction, and where the lines are pseudo-randomly sampled: central lines are constantly acquired and the sampling density decreases as the lines are far from the center. Application on real speech data show that the framework enables dynamic sequences of vocal tract images to be recovered at a framerate higher than 30 frames per second and with a spatial resolution of 1 mm. A method to extract articulatory data from contour identification is presented. It is intended, in fine, to be used for the creation of a large database of articulatory data.

Copy-synthesis of phrase-level utterances

This paper presents a simulation framework for synthesizing speech from anatomically realistic data of the vocal tract. The acoustic propagation paradigm is appropriately chosen so that it can deal with complex geometries and a time-varying length of the vocal tract. The glottal source model designed in this paper allows partial closure of the glottis by branching a posterior chink in parallel to a classic lumped mass-spring model of the vocal folds. Temporal scenarios for the dynamic shapes of the vocal tract and the glottal configurations may be derived from the simultaneous acquisition of X-ray images and audio recording. Copy synthesis of a few French sentences shows the accuracy of the simulation framework to reproduce acoustic cues of natural phrase-level utterances containing most of French natural classes while considering the real geometric shape of the speaker.