Showing papers by "Grenoble Institute of Technology published in 1998"

Towards an audiovisual virtual talking head: 3d articulatory modeling of tongue, lips and face based on mri and video images

Abstract: A linear three-dimensional articulatory model of tongue, lips and face is presented. The model is based on a linear component analysis of the 3D coordinates defining the geometry of the different organs, obtained from Magnetic Resonance Imaging of the tongue, and from front and profile video images of the subject's face marked with small beads. In addition to a common jaw height parameter, the tongue is controlled by five parameters while the lip and face are driven by four parameters, that can be interpreted in phonetic / articulatory terms. This model has been finally integrated into the ICP virtual talking head.

Nanoscale Hardening Precipitiation in AlMgSi Alloys: A Transmission Electron Microscopy and Small‐Angle Neutron Scattering Study

Abstract: Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) have been used to study hardening precipitation in a 6056 Al–Mg–Cu–Si alloy at peak ageing. TEM observations revealed that the precipitates adopt rod and lath morphologies. A TEM image analysis, using group-symmetry properties, revealed that the precipitates belong to the orthorhombic (2/m 2/m 2/m) point group. The SANS data analysis, based on a log-normal model, yields the distribution and mean size of the rod precipitates.

Audiovisual Speech Coder : Using Vector Quantization To Exploit The Audio/Video Correlation.

Abstract: Visual information can help listeners to better understand what is said. In the speech coding domain, it will be shown that it allows to reduce the transmission rate of a classic vocoder (1,9 kbit/s instead of 2,4 kbit/s) by estimating audio parameters from video ones. In addition, vector quantization seems to be a good method to reduce the redundancy between some audio and visual coefficients. With the vector quantization, we can reduce again the bit rate while decreasing the quantization error.

Miniaturized deformable magnetic mirror for adaptive optics

Abstract: An alternative approach to more compact deformable mirrors for adaptive optics is developed. A thin and flexible reflective membrane is coated with a magnetic layer and locally deformed by the field created by an array of planar microcoils. This novel technology should enable higher resolution with smaller, lighter integrated mirrors. Several complementary modeling tools are used to study the electromagnetic, mechanical, magneto-mechanical and thermal behavior of the device. A first prototype of (phi) 30 mm mirror with a matrix of permanent magnets and an array of 25 microcoils is under construction.

Glass electro-optic polymer structure for light modulation and switching

Abstract: A novel hybrid structure for optical modulation and switching is presented. It consists of a thin film of electro-optic polymer spin-coated on passive waveguide made by ion exchange on glass substrate. Two structures corresponding to weak guiding and strong guiding conditions are considered. Design issues and modulation performances are studied for the two structures. Low half-wave voltages less than 10 volts are expected for an interaction length of 1 cm provided the electro-optic coefficient of the nonlinear polymer is 10 pm/V.

Reiterant speech for the evaluation of natural vs. synthetic prosody.

Abstract: This work deals with some evaluation experiments on reiterant speech using both synthetic and natural stimuli. They have been designed to test the efficiency of the described paradigm to diagnose the adequacy of synthetic prosody to syntactic structure in reference with natural performances. Following a general methodology developed for synthesis [7], experiments have been conducted on the ICP synthetic prosody with the aim of validating the original corpus from which the prosodic model was learned .

Texture and Microstrucutre of Cu and CuZn37 Brass under Shearing in a Planar Shear Test

Abstract: The shearing in the plane of a sheet and up to the point of final rupture was performed by means of shear apparatus on samples of copper and CuZn37 brass preliminary cold rolled to 75% reduction of area Optical examination of strain markings in Cu samples has revealed the formation of regular shear zones; on the contrary, non-regular and stepped shear zones were observed in the case of CuZn37 brass. Crystallographic textures determined by X-ray pole figure method have revealed increasing dispersion of the crystallite orientation for both examined cases; the number of crystallites rotating around the direction of shearing increases. Microstructural observation of sheared samples of copper has shown the formation of cellular structure of dislocation elongated in the shear direction; in the case of brass we note the shear banding on the background of twin + matrix sets.

Recovering Gestures From Speech Signals: A Preliminary Study for Nasal Vowels

Abstract: For nasal vowels, a gesture as simple as the lowering of the velum produces complex acoustic spectra. However, we still find a relative simplicity in the perceptual space; nasality is perceived easily. In this preliminary study, we use statistic method to recover the gesture of the velum. In order to reduce the extreme variability of nasal vowels, we introduced a simulation based on Maeda’s model instead of using a natural speech signal. In previous studies, nasality is supposed to increase either with size of the nasal area or with the area ratio between nasal and oral tracts at the extremity of the velum. In this work, both types of data are considered and analyzed with linear and non-linear tools. Finally, statistic inference is described and results are given for various areas of the nasal tract entrance and for various area ratios. The results show that velar port area is correctly estimated for small values while area ratio is a better parameter when velar port area increases. 1. ABOUT NASAL VOWELS About 20 % of the UPSID languages have a phonemic contrast between oral vowels and nasal vowels. In French nasality is the only distinctive feature between the words [pe] paix (peace) and [pe~] pain (bread). Nasal vowels often derive from nasal consonant assimilation. This phenomenon also exists in languages with nasal consonants, more or less pronounced according to the context. Such vowels are called nasalized vowels in order to discriminate from nasal vowels. Nasalization, controlled or not, is a widespread feature. On the articulatory level, vowel nasalization is produced by the lowering of the velum. This simple gesture connects the nasal fossa to the oral tract. The nasal fossa are quite complex and very different from one to another (Dang & Honda, 1994), but they are fixed for a given person. Acoustic consequences of this gesture depend on each person and also on the position of the velum. Many studies tried to find the acoustic correlates of nasality. Most of these agrees with a relative weakness of the first formant and proposes other secondary correlates. However detailed characteristics of the spectra of nasal vowels vary with the frequency of the first oral resonance and the magnitude of nasal coupling. In spite of such acoustic complexity, listeners give similar vowels nasality judgements, regardless of the phonological status of nasalization in their native language (Beddor & Strange, 1982). Articulatory-to-acoustic relationship is quite complex and still not well understood for nasal vowels. Until now, there has been no corpus of velar port size measurements with simultaneous speech signal. The velum is an internal organ difficult of access. Nowadays IRM can very useful static vocal tract data. Furthermore, articulatory-acoustic inversion projects such as SPEECHMAPS have provided tools, data and encouraging results on oral vowels and fricative consonants. Can inversion techniques estimate the position of the velum or its evolution during nasal vowel production ? In this preliminary study, we tried to answer this question in simplified and controlled conditions. Instead of natural speech signal, vocal tract simulation produces acoustic transfer functions. First, the production model and corresponding database are presented. Then database analyses are given before explaining in the third section the inversion technique applied and the results obtained. 2. PRODUCTION MODEL OF NASAL VOWELS 2.1. Articulatory Model Usually articulatory models proposed by Maeda (1988) and Mermelstein (1973) consider only the oral tract. The model used in this work is Maeda’s model based on X-ray images of a speaker (Patricia Barbier) pronouncing French sentences. Eight parameters regulate the jaw and tongue positions, the opening and the protrusion of the lips, the larynx length. A ninth parameter vm is introduced to represent the velum position. Then, the articulatory model calculates the vocal tract area function whatever the value of the parameter vm may be, as if the velar port was closed. In Maeda’s model, all parameters are normalised, centred on zero which corresponds to the mean value of all the positions registered on X-ray images and with a standard deviation 1. For normal distributions, variations between –3 and 3 are supposed to cover most of the cases. A more detailed study of the parameter vm is needed to check that it has a normal distribution. The distribution of all the values of parameter vm measured on X-ray images brings to the fore that this parameter does not follow such a distribution. The lowest values are around –1 and they are obtained during plosive consonant production. When parameter vm is between –1 and 0, the velar port is closed. The highest values are close to 3 or 4 and correspond to the rest position, nasal vowels or consonants. The default value 0 is used for the oral vowel production, the velar port area is null. When parameter vm increases, the velum lowers and allows the air to go through the nasal fossa. The velum is 1 cm thick and is ending by the uvula. Both outlines of X-ray image and midsagittal section obtained by the model are shown in Figure 1. So this articulatory model enables to get both oral area function and velar port area, areas being calculated from midsaggital sections. As data about Patricia Barbier’s nasal Figure 1 : Example of the outlines of a X-ray image and the outlines of the midsaggital section associated. fossa are not available, area functions of nasal tract and sinuses are given by Feng and Castelli (1996). A set of nine parameters controls configurations of the vocal tract and corresponding area function. As this study only concerns vowels, constraints are imposed on the constriction area, the place of constriction and the lips area. 2.2 Construction of the Database Traditionally simulation studies of nasal vowels compare transfer functions obtained with different velar port area, called hereafter nasal area An. The nasal area variations when parameter vm increases are studied for various configurations. A bijective relation exists between the parameter vm and the nasal area An except for high values of vm where there is a saturation which depends on the tongue position. The velum lowers until it rests on the tongue and stays in that position even if parameter vm still increases. Without taking into account such a saturation, the seven values corresponding to the nasal area values of 0, 0.2, 0.4, 0.8, 1.8, 2.2, 2.4, 2.6 cm2 are determined. For a null value of parameter vm, 1000 configurations are at random and transfer functions are computed for each of the seven values of parameter vm. This database contains thus 7000 transfer functions. However we cannot ignore nasal area saturation; for the same high value of parameter vm, the nasal areas An can be very different because of the tongue position. To avoid such vowel dependence, Feng proposed to use another parameter: the area ratio d (Feng & Castelli, 1996).