VOWELS IN STANDARD AUSTRIAN GERMAN - Acoustics ...

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Sylvia Moosmüller most distinctive formant transitions. This also means that the vocal tract is quantal in its nature. It has been put forward that the DRM model implicitly assumes that a linear relation between articulation and acoustic output exists (Boë & Perrier 1990). Linearity is, however, more a goal of the model than an assumption; the constriction locations are placed at the midpoints of each region, where transversal displacements guarantee maximal formant frequency changes, so as to optimize the principle to achieve maximal contrast with minimal area deformation (least effort principle): “An important property of the model is that variation in the values of the regions’ crosssectional areas around the uniform-tube configuration generates maximal formant frequency variations. In other words, if we look for places in the vocal tract having the best modulation of formant frequencies around the uniform configuration, and the largest dynamics of these modulations, these places are around the midpoints of the regions. Nonlinearities and saturations occur only near the borders of the vocalic space.” (Carré & Mrayati 1991: 436f) Areas of stability, in this model, are not exploited in production. In order to examine whether areas of stability are exploited or not, one has to know which area functions result in an identical acoustic output. Atal et al. (1978) introduced the concept of fibers, which defines vocal tract shapes with identical acoustic properties. The authors conclude: “Large changes in the shape of the vocal tract can be made wihout changing the formant frequencies. These changes are consistent with the hypothesis that compensatory articulation is a possibility–that is, different people can produce the same sound with different vocal-tract shapes.” (Atal et al 1978: 1555) Although “an area function is not in itself an articulatory parameter” (Boë et al 1992: 29, but see also Wood 1991a), it is possible to derive to a certain extent vocal tract adjustments from the speech signal (Boë et al 1992, Ladefoged et al. 1978). Boë et al. (1992) reduced the possible area functions to meaningful configurations and could classify 7 out of 10 vowels uniquely. The vowels [i, e, a, y, o, O] show a relatively precise control of the constriction location and of constriction degree. [i, y, e] show a strong constraint and maintain a small constriction degree (Ac < 1 cm 2 ). The vowels [E, 46
47 Vowels in Standard Austrian German ë, ê] exhibit a large variation in constriction degree (from 0.2 cm 2 to 4.0 cm 2 ). The authors conclude: “The parameters Xc, Ac and Al thus seem to be good candidates for use in inversion procedures. It must be noted though that the precision of control necessary for each parameter depends on acoustic sensitivities, which vary according to the vowel under consideration (…). Thus [i] requires precise control of Xc, but no precision at all for Al. The case of [u] is different, requiring a very small and accurate lip opening, but granting more latitutde for Ac.” (Boë et al. 1992: 36) Again, the degree of freedom guaranteed for either Al in [i] or Ac in [u] need not be reflected in actual articulatory adjustments. On the contrary, Wood (1982: 46) could show that Al is precisely controlled in the front vowels: the jaw opening is smaller than 8,9 mm for the i-vowels, but greater than 8,9 mm for the e-vowels. These results were confirmed by Hoole & Mooshammer (2002). Regions of stability, which in principle allow for a certain degree of freedom of articulatory adjustments, exist. Given the high degree of precision in the articulation of (vowel) phonemes, it is not quite clear what their function is. In quantal theory, regions of acoustic stability are separated by regions of acoustic instability, and these natural boundaries define the opposition between distinctive features (Stevens 2003). The boundary, e.g. between [+back] and [-back] vowels, occurs at a location where F2 is near the lowest frequency of the subglottal system and the interaction between the sub- and supraglottal resonances cause discontinuous jumps in the spectrum (Stevens 2003). This is certainly a conclusive explanation for the rough division of [+back] and [-back] vowels. Such a natural boundary is not always provided by quantal theory however (e.g. within the front region). On the contrary, quantal theory predicts a high stability of the vowel /i/. This has already been confuted by Abry et al. (1989). The current investiga- tion reveals that in Standard Austrian German, the /i/ vowels are located exactly at or slightly before such a natural boundary where formant frequencies converge and a slight displacement of the tongue position or a reduction in constriction length causes a considerable change in formant frequency values, especially F3. Therefore, the stability
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VOWELS IN STANDARD AUSTRIAN GERMAN
Page 3 and 4: Vowels in Standard Austrian German
Page 9 and 10: 1. Introduction: Setting the Theore
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Page 59 and 60: 4. Vowel inventory and features 51
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Page 77 and 78: Height 0 10 20 30 40 u i o ö ü e
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5.3. Processes vs. Coarticulation 1
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� F3 shows a high variability in
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c(xmin, xmax) 0.000 0.001 0.002 0.0
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6.2. Undershoot vs. Processes 179 V
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Therefore, it can be observed that
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c(xmin, xmax) 0.00 0.02 0.04 0.06 0
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Variability coefficient 40,000 35,0
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6.6.3.4. The vowel /E/ 215 Vowels i
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6.6.3.6. The vowel /u/ 217 Vowels i
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z-score 5,00 4,00 3,00 2,00 1,00 0,
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Appendix 269 Vowels in Standard Aus
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