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Abstract:
Low dimensional and speaker-independent linear vocal tract
parametrizations can be obtained using the 3-mode PARAFAC factor
analysis procedure first introduced by Harshman et al. (1977).
The following study used PARAFAC to investigate the stress
distinction in German vowel production. Tongue movements of six
German speakers were recorded by means of EMMA. The speech
material consisted of the 15 German vowels, recorded in /t/-
context. Our corpus includes these vowels in stressed and
unstressed position. They were entered into the classical
PARAFAC1 model treating the stress distinction for each subject
as two different speakers. This gave a reasonable 2-factor
solution, but was not without drawbacks. The model turned out to
be capable of recovering gross anatomical properties of our
subjects, but failed to return intraindividual differences in
tongue shapes with respect to word stress. This indicated that
the strict linearity assumptions required in the classical
PARAFAC model were too strong to capture stress-specific
variation in full detail. We supposed that a model closely
related to PARAFAC, PARAFAC2, should allow to account for
systematic variation produced by word stress by imposing weaker
structure on the data. As will be shown, PARAFAC2 modeled the
physical properties of the vocal tract shape in a more realistic
and plausible way.
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