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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.
As has been noted previously, speakers with coronally low "flat" palates exhibit less articulatory variability than speakers with coronally high "domeshaped" palates. This phenomenon is investigated by means of a tongue model and an EPG experiment. The results show that acoustic variability depends on the shape of the vocal tract. The same articulatory variability leads to more acoustic variability if the palate is flat than if it is domeshaped. Furthermore, speakers with domeshaped palates show more articulatory variability than speakers with flat palates. The results are explained by different control strategies by the speakers. Speakers with flat palates reduce their articulatory variability in order to keep their acoustic variability low.
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.
Temporal development of compensation strategies for perturbed palate shape in German /S/-production
(2006)
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.
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.
Two hypotheses have been proposed in order to account for velar softening, i.e., a process through which /k/ changes to an affricate. Whereas one hypothesis states that for the process to apply the velar stop has to be realized as an (alveolo) palatal stop (articulation-based hypothesis), the other claims that velar softening is triggered by acoustic similarity between the input and output segments (acoustic equivalence hypothesis). The present paper investigates the acoustic equivalence hypothesis by comparing several acoustic properties of /k/ in various vowel contexts with those of /ts , ts , tc / for three languages differing in stop burst aspiration, i.e., German, Polish and Catalan. Results suggest that the acoustic equivalence hypothesis could account for velar softening in aspirated velar stops but not in unaspirated velar stops. The results also provide an explanation as to why aspirated velar stops are prone to undergo softening more easily when followed by front vocalic segments than in other contexts and positions
This paper shows that several typologically unrelated languages share the tendency to avoid voiced sibilant affricates. This tendency is explained by appealing to the phonetic properties of the sounds, and in particular to their aerodynamic characteristics. On the basis of experimental evidence it is shown that conflicting air pressure requirements for maintaining voicing and frication are responsible for the avoidance of voiced affricates. In particular, the air pressure released from the stop phase of the affricate is too high to maintain voicing, which in consequence leads to a devoicing of the frication part.
A model is proposed that interprets a variety of connected speech processes as resulting from prosodic modulations at different tiers of functional speech motor control along the hypo-hyper dimension [10]. The general background of the model is given by the trichotomy of A-, B- and C-prosodic phenomena [15] that together constitute the acoustic makeup of any speech utterance (with regard to their respective time domains at the uttarance/phrase level, the syllabic level and the segmental level).
Bilabial stops undergoing Surface Palatalization (SP) were analyzed in an EMMA/EPG study. Articulatorily, the point of maximal palatal contact and the labial opening movement were analyzed. The acoustic analysis pertained to stop related timing and the point of the highest F2-value. Results show (i) that SP yields a higher F2 at vowel onset and a lengthened opening gesture and (ii) that morphemeinduced palatalizations are distinguished from word initial ones and sandhi-palatalizations articulatorily and acoustically by a shorter delay of palatal target position with respect to stop production; (iii) no differences are found between ‘repalatalized’ and plain segments in case of sandhi palatalization.
The present study poses the question on what phonetic and phonological grounds postalveolar fricatives in Polish can be analyzed as retroflex and whether postalveolar fricatives in other Slavic languages are retroflex as well. Velarization and incompatibility with front vowels are introduced as articulatory criteria for retroflexion, based on crosslinguistic data. According to these criteria, Polish and Russian have retroflex fricatives, whereas Bulgarian and Czech do not. In a phonological representation of these Slavic retroflexes, the necessity of perceptual features is shown. Lastly, it is illustrated that palatalization of retroflex fricatives both in Slavic languages and more generally causes a phonetic and phonological change to a non-retroflex sound.