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This work investigates laryngeal and supralaryngeal correlates of the voicing contrast in alveolar obstruent production in German. It further studies laryngealoral co-ordination observed for such productions. Three different positions of the obstruents are taken into account: the stressed, syllable initial position, the post-stressed intervocalic position, and the post-stressed word final position. For the latter the phonological rule of final devoicing applies in German. The different positions are chosen in order to study the following hypotheses:
1. The presence/absence of glottal opening is not a consistent correlate of the voicing contrast in German.
2. Supralaryngeal correlates are also involved in the contrast.
3. Supralaryngeal correlates can compensate for the lack of distinction in laryngeal adjustment.
Including the word final position is motivated by the question whether neutralization in word final position would be complete or whether some articulatory residue of the contrast can be found.
Two experiments are carried out. The first experiment investigates glottal abduction in co-ordination with tongue-palate contact patterns by means of simultaneous recordings of transillumination, fiberoptic films and Electropalatography (EPG). The second experiment focuses on supralaryngeal correlates of alveolar stops studied by means of Electromagnetic Articulography (EMA) simultaneously with EPG. Three German native speakers participated in both recordings. Results of this study provide evidence that the first hypothesis holds true for alveolar stops when different positions are taken into account. In fricative production it is also confirmed since voiceless and voiced fricatives are most of the time realised with glottal abduction. Additionally, supralaryngeal correlates are involved in the voicing contrast under two perspectives. First, laryngeal and supralaryngeal movements are well synchronised in voiceless obstruent production, particularly in the stressed position. Second, supralaryngeal correlates occur especially in the post-stressed intervocalic position. Results are discussed with respect to the phonetics-phonology interface, to the role of timing and its possible control, to the interarticulatory co-ordination, and to stress as 'localised hyperarticulation'.
Four speakers repeated 8 times 15 sentences containing 'pVp' syllables (V being /a/, /i/ and /u/). The 'pVp' syllables were located in final, penultimate and antepenultimate position relatively to the Intonational Phrase (IP) boundary. They were embedded in lexical words of 1-3 syllables and were either word-initial or word-final. Results show that the closer the vowel in word-final position is to the IP boundary, the longer the duration and the higher the fundamental frequency of the vowel; it is also characterised by larger lip opening gestures. The potential reduction or coarticulation of vowels in wordinitial position compared to their counterparts in word-final position is discussed.
Articulatory token-to-token variability not only depends on linguistic aspects like the phoneme inventory of a given language but also on speaker specific morphological and motor constraints. As has been noted previously (Perkell (1997), Mooshammer et al. (2004)), speakers with coronally high "domeshaped" palates exhibit more articulatory variability than speakers with coronally low "flat" palates. One explanation for that is based on perception oriented control by the speaker. The influence of articulatory variation on the cross sectional area and consequently on the acoustics should be greater for flat palates than for domeshaped ones. This should force speakers with flat palates to place their tongue very precisely whereas speakers with domeshaped palates might tolerate a greater variability. A second explanation could be a greater amount of lateral linguo-palatal contact for flat palates holding the tongue in position. In this study both hypotheses were tested.
In order to investigate the influence of the palate shape on the variability of the acoustic output a modelling study was carried out. Parallely, an EPG experiment was conducted in order to investigate the relationship between palate shape, articulatory variability and linguo-palatal contact.
Results from the modelling study suggest that the acoustic variability resulting from a certain amount of articulatory variability is higher for flat palates than for domeshaped ones. Results from the EPG experiment with 20 speakers show that (1.) speakers with a flat palate exhibit a very low articulatory variability whereas speakers with a domeshaped palate vary, (2.) there is less articulatory variability if there is lots of linguo-palatal contact and (3.) there is no relationship between the amount of lateral linguo-palatal contact and palate shape. The results suggest that there is a relationship between token-to-token variability and palate shape, however, it is not that the two parameters correlate, but that speakers with a flat palate always have a low variability because of constraints of the variability range of the acoustic output whereas speakers with a domeshaped palate may choose the degree of variability. Since linguo-palatal contact and variability correlate it is assumed that linguo-palatal contact is a means for reducing the articulatory variability.
This paper describes the processing of MRI and CT images needed for developing a 3D linear articulatory model of velum. The 3D surface that defines each organ constitutive of the vocal and nasal tracts is extracted from MRI and CT images recorded on a subject uttering a corpus of artificially sustained French vowels and consonants. First, the 2D contours of the organs have been manually extracted from the corresponding images, expanded into 3D contours, and aligned in a common 3D coordinate system. Then, for each organ, a generic mesh has been chosen and fitted by elastic deformation to each of the 46 3D shapes of the corpus. This has finally resulted in a set of organ surfaces sampled with the same number of 3D vertices for each articulation, which is appropriate for Principal Component Analysis or linear decomposition. The analysis of these data has uncovered two main uncorrelated articulatory degrees of freedom for the velum's movement. The associated parameters are used to control the model. We have in particular investigated the question of a possible correlation between jaw / tongue and velum's movement and have not find more correlation than the one found in the corpus.
In order to investigate the articulatory processes of the hasty and mumbled speech of clutterers, the kinematic variability was analysed by means of electromagnetic midsagittal articulography (EMMA). In contrast to stutterers, clutterers improve their intelligibility by concentrating on their speech task. Variability is an important criterion in comparable studies of stuttering and is discussed in terms of the stability of the speech motor system. The aim of the current study was to analyse the spatial and temporal variability in the speech of three clutterers and three control speakers. All speakers were native speakers of German. The speech material consisted of repetitive CV-syllables and foreign words, because clutterers have the most severe problems with long words which have a complex syllable structure. The results showed a higher quotient of variation for clutterers in the foreign word production. For the syllable repetition task, no significant differences between clutterers and controls were found. The extremely large and variable displacements were interpreted as a strategy that helps clutterers to improve the intelligibility of their speech.
A visual articulatory model and its application to therapy
of speech disorders : a pilot study
(2005)
A visual articulatory model based on static MRI-data of isolated sounds and its application in therapy of speech disorders is described. The model is capable of generating video sequences of articulatory movements or still images of articulatory target positions within the midsagittal plane. On the basis of this model (1) a visual stimulation technique for the therapy of patients suffering from speech disorders and (2) a rating test for visual recognition of speech movements was developed. Results indicate that patients produce recognition rates above level of chance already without any training and that patients are capable of increasing their recognition rate over the time course of therapy significantly.
We measure face deformations during speech production using a motion capture system, which provides 3D coordinate data of about 60 markers glued on the speaker's face. An arbitrary orthogonal factor analysis followed by a principal component analysis (together called a guided PCA) of the data has showed that the first 6 factors explain about 90% of the variance, for each of our 3 speakers. The 6 derived factors, therefore, allow us to efficiently analyze or to reconstruct with a reasonable accuracy the observed face deformations. Since these factors can be interpreted in articulatory terms, they can reveal underlying articulatory organizations. The comparison of lip gestures in terms of data derived factors suggests that these speakers differently maneuver the lips to achieve contrast between /s/ and /R/. Such inter-speaker variability can occur because the acoustic contrast of these fricatives is shaped not only by the lip tube but also by cavities inside the mouth such as the sublingual cavity. In other words, these tube and cavity can acoustically compensate each other to produce their required acoustic properties.
In order to understand the functional morphology of the human voice producing system, we are in need of data on the vocal tract anatomy of other mammalian species. The larynges and vocal tracts of four species of Artiodactyla were investigated in combination with acoustic analyses of their respective calls. Different evolutionary specializations of laryngeal characters may lead to similar effects on sound production. In the investigated species, such specializations are: the elongation and mass increase of the vocal folds, the volume increase of the laryngeal vestibulum by an enlarged thyroid cartilage and the formation of laryngeal ventricles. Both the elongation of the vocal folds and the increase of the oscillating masses lower the fundamental frequency. The influence of an increased volume of the laryngeal vestibulum on sound production remains unclear. The anatomical and acoustic results are presented together with considerations about the habitats and the mating systems of the respective species.
Studying kinematic behavior in speech production is an indispensable and fruitful methodology in order to describe for instance phonemic contrasts, allophonic variations, prosodic effects in articulatory movements. More intriguingly, it is also interpreted with respect to its underlying control mechanisms. Several interpretations have been borrowed from motor control studies of arm, eye, and limb movements. They do either explain kinematics with respect to a fine tuned control by the Central Nervous System (CNS) or they take into account a combination of influences arising from motor control strategies at the CNS level and from the complex physical properties of the peripheral speech apparatus. We assume that the latter is more realistic and ecological. The aims of this article are: first, to show, via a literature review related to the so called '1/3 power law' in human arm motor control, that this debate is of first importance in human motor control research in general. Second, to study a number of speech specific examples offering a fruitful framework to address this issue. However, it is also suggested that speech motor control differs from general motor control principles in the sense that it uses specific physical properties such as vocal tract limitations, aerodynamics and biomechanics in order to produce the relevant sounds. Third, experimental and modelling results are described supporting the idea that the three properties are crucial in shaping speech kinematics for selected speech phenomena. Hence, caution should be taken when interpreting kinematic results based on experimental data alone.