561 research outputs found
The influence of the palate shape on articulatory token-to-token variability
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
Articulatory optimisation in perturbed vowel articulation
A two-week perturbation EMA-experiment was carried out with palatal prostheses. Articulatory effort for five speakers was assessed by means of peak acceleration and jerk during the tongue tip gestures from /t/ towards /i, e, o, y, u/. After a period of no change speakers showed an increase in these values. Towards the end of the experiment the values decreased. The results are interpreted as three phases of carrying out changes in the internal model. At first, the complete production system is shifted in relation to the palatal change, afterwards speakers explore different production mechanisms which involves more articulatory effort. This second phase can be seen as a training phase where several articulatory strategies are explored. In the third phase speakers start to select an optimal movement strategy to produce the sounds so that the values decrease
Motor equivalent strategies in the production of /u/ in perturbed speech
Several articulatory strategies are available during the production of /u/, all resulting in a similar acoustic output. /u/ has two main constrictions, at the velum and at the lips. A perturbation of either constriction can be compensated at the other one, e.g wider constriction at the velum by more lip protrusion, wider lip opening by more tongue retraction. This study investigates whether speakers use this relation under perturbation. Six speakers were provided with palatal prostheses which were worn for two weeks. Speakers were instructed to make a serious attempt to produce normal speech. Their speech was recorded via EMA and acoustics several times over the adaptation period. Formant values of /u/-productions were measured. Velar constriction width and lip protrusion were estimated. For four speakers a correlation between constriction width and lip protrusion was found. A negative correlation between lip protrusion and F1 or F2 could sometimes be observed, but no correlation occurred between constriction size and either of the formants. The results show that under perturbation speakers use motor equivalent strategies in order to adapt. The correlation between constriction size and lip protrusion is stronger than in studies investigating unperturbed speech. This could be because under perturbation speakers are inclined to try out several strategies in order to reach the acoustic target and the co-variability might thus be greater
A 3D biomechanical vocal tract model to study speech production control: How to take into account the gravity?
This paper presents a modeling study of the way speech motor control can deal
with gravity to achieve steady-state tongue positions. It is based on
simulations carried out with the 3D biomechanical tongue model developed at
ICP, which is now controlled with the Lambda model (Equilibrium-Point
Hypothesis). The influence of short-delay orosensory feedback on posture
stability is assessed by testing different muscle force/muscle length
relationships (Invariant Characteristics). Muscle activation patterns necessary
to maintain the tongue in a schwa position are proposed, and the relations of
head position, tongue shape and muscle activations are analyzed
Modeling the production of VCV sequences via the inversion of a biomechanical model of the tongue
A control model of the production of VCV sequences is presented, which
consists in three main parts: a static forward model of the relations between
motor commands and acoustic properties; the specification of targets in the
perceptual space; a planning procedure based on optimization principles.
Examples of simulations generated with this model illustrate how it can be used
to assess theories and models of coarticulation in speech
The use of sensory feedback in the adaptation of perturbed /s/
The study investigates the contribution of tactile and auditory feedback in the adaptation of /s/ towards a palatal prosthesis. Five speakers were recorded via electromagnetic articulography, at first without the prosthesis, then with the prosthesis and auditory feedback masked, and finally with the prosthesis and auditory feedback available. Tongue position, jaw position and acoustic centre of gravity of productions of the sound were measured. The results show that the initial adaptation attempts without auditory feedback are dependent on the prosthesis type and directed towards reaching the original tongue palate contact pattern. Speakers with a prosthesis which retracted the alveolar ridge retracted the tongue. Speakers with a prosthesis which did not change the place of the alveolar ridge did not retract the tongue. All speakers lowered the jaw. In a second adaptation step with auditory feedback available speakers reorganised tongue and jaw movements in order to produce more subtle acoustic characteristics of the sound such as the high amplitude noise which is typical for sibilants
A Muscle Model Based on Feldman's Lambda Model: 3D Finite Element Implementation
This paper presents the introduction of Feldman's muscle model in a three
dimensional continuum finite element model of the human face. This model is
compared to the classical Hill-type muscle modelComment: CMBBE'2013, Salt Lake City : United States (2013
Temporal development of compensation strategies for perturbed palate shape in German /S/-production
The palate shape of four speakers was changed by a prosthesis which either lowered the palate or retracted the alveoles. Subjects wore the prosthesis for two weeks and were recorded several times via EMA. Results of articulatory measurements show that speakers use different compensation methods at different stages of the adaptation. They lower the tongue immediately after the insertion of the prosthesis. Other compensation methods as for example lip protrusion are only acquired after longer practising periods. The results are interpreted as supporting the existence of different mappings between motor commands, vocal tract shape and auditory-acoustic target
Modeling the consequences of tongue surgery on tongue mobility
This paper presents the current achievements of a long term project aiming at
predicting and assessing the impact of tongue and mouth floor surgery on tongue
mobility. The ultimate objective of this project is the design of a software
with which surgeons should be able (1) to design a 3D biomechanical model of
the tongue and of the mouth floor that matches the anatomical characteristics
of each patient specific oral cavity, (2) to simulate the anatomical changes
induced by the surgery and the possible reconstruction, and (3) to
quantitatively predict and assess the consequences of these anatomical changes
on tongue mobility and speech production after surgery
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