International audience

Tongue shape reconstruction based on safe and convenient measurement techniques is of great interest for speech research and speech therapy. Two potentially useful and related measurement techniques for this purpose are electropalatography (EPG) and optopalatography (OPG). While EPG measures the time-varying contact pattern between the hard palate and the tongue, OPG measures distances between the two. Here, we examined the potential of EPG, OPG, and their combination for predicting the whole tongue contour using a multiple linear regression model. The model was trained and tested with tongue shapes and virtual sensor data obtained from Magnetic Resonance Images of sustained articulations of two speakers. When the model was trained and tested with the same speaker, the error of tongue contour reconstruction was significantly lower for predictions based on OPG data than for predictions based on EPG data. When the model was trained with one speaker and tested with the other, the error pattern was less consistent and the overall error was higher. Hence, especially OPG is well suited for tongue contour prediction, but an adaptation method is needed to transfer the model to a new speaker.

This paper presents an animated 2D articulation model of the tongue and the lips for biofeedback applications. The model is controlled by real-time optopalatographic measurements of the positions of the upper lip and the tongue in the anterior oral cavity. The measurement system is an improvement on a previous prototype with increased spatial resolution and an enhanced close-range behavior. The posterior part of the tongue was added to the model by linear prediction. The prediction coefficients were determined and evaluated using a corpus of vocal tract traces of 25 sustained phonemes. The model represents the tongue motion and the lip opening physiologically plausible during articulation in real-time. Index Terms: optopalatography, glossometry, linear prediction, animated vocal tract model, biofeedback

This paper describes the development of a device that combines the electropalatographic measurement of tongue-palate contact with optical distance sensing to measure the mid-sagittal contour of the tongue and the position of the lips. The device consists of a thin acrylic pseudopalate that contains both contact sensors and optical reflective sensors. Application areas are, for example, experimental phonetics, speech therapy, and silent speech interfaces. With regard to the latter, the prototype of the system was applied to the recognition of vowels from the sensor signals. It was shown that a classifier using the combined input data from both the contact sensors and the optical sensors had a higher recognition rate than classifiers based on only one type of sensory input.

Two-mass models of the vocal folds and their variants are valuable tools for voice synthesis and analysis, but are not able to produce breathy voice qualities. The produced voice qualities usually lie between normal and pressed. The reason for this property is that the mass elements are aligned parallel to the dorso-ventral axis. Thereby, the glottis always closes simultaneously along the entire length of the vocal folds. For breathy phonation, however, the closure happens rather gradual. This article introduces a modified two-mass model with mass elements that are inclined with respect to the dorso-ventral axis as a function of the degree of abduction. In this way, the closing phase of the glottis becomes progressively more gradual when the degree of abduction is increased. This model is able to produce the continuum of voice qualities from pressed over normal to breathy voices.

We present the first prototype of a new optoelectronic instrument for the combined real-time measurement of the tongue contour in the mid-sagittal plane, the contact pattern between the tongue and the palate, and the position of the lips. The instrument consists of a thin acrylic pseudopalate with embedded contact sensors, as for electropalatography, and optical distance sensors to measure tongue-palate distances, as for glossometry. One additional distance sensor is located at the anterior side of the upper incisors to register the degree of opening and protrusion of the lips. Together, the sensors provide complementary information about the articulation of vowels and consonants, which was verified in initial experiments. The instrument offers new perspectives for the study of normal and disordered speech production, as well as for silent speech interfaces and speech prostheses for laryngectomees.

We present a novel quantitative model for the generation of articulatory trajectories based on the concept of sequential target approximation. The model was applied for the detailed reproduction of movements in repeated consonant-vowel syllables measured by electromagnetic articulography (EMA). The trajectories for the constrictor (lower lip, tongue tip, or tongue dorsum) and the jaw were reproduced. Thereby, we tested the following hypotheses about invariant properties of articulatory commands: (1) The target of the primary articulator for a consonant is invariant with respect to phonetic context, stress, and speaking rate. (2) Vowel targets are invariant with respect to speaking rate and stress. (3) The onsets of articulatory commands for the jaw and the constrictor are synchronized. Our results in terms of high-quality matches between observed and model-generated trajectories support these hypotheses. The findings of this study can be applied to the development of control models for articulatory speech synthesis.

Virtual articulatory targets are a concept to explain the different trajectories of primary and secondary articulators during consonant production, as well as the different places of the tongue-palate contact depending on the context vowel, for example in [igi] vs. [ugu]. The virtual targets for the tongue tip and the tongue body in apical and dorsal plosives are assumed to lie above the palate, and for bilabial consonants, the target is a negative degree of lip opening. In the present study, we discuss the concept of virtual targets and its application for articulatory speech synthesis. In particular, we examined how the location of virtual targets affects the acoustics and intelligibility of synthetic plosive-vowel syllables. It turned out that virtual targets that lie about 10 mm beyond the consonantal closure location allow a more precise reproduction of natural speech signals than virtual targets at a distance of about 1 mm. However, we found no effect on the intellegibility of the consonants.

A comprehensive neural model of speech motor control including a three dimensional articulatory speech synthesizer as a front-end device is described in detail in this paper.The training of the sensory-to-motor mappings -which can be interpreted as the prelinguistic phase of speech acquisition -is described in detail for quasi-static as well as for dynamic articulation.