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ISCApad #205 |
Wednesday, July 08, 2015 by Chris Wellekens |
A View from Dresden onto the History of Speech Communication
Part 5: Artificial vocal fold models – The investigation of phonation The investigation of the larynx was (and is) one of the predominant topics in phonetic research. In the early times of experimental phonetics, mechanical models of the larynx or, at least, of the vocal folds have been utilized according to the paradigm of analysis-by-synthesis.
The first models used flat parallel elastic membranes or other simple elements to simulate the function of the vocal folds (Fig. 1). However, the geometry of these models was rather different from that of real human vocal folds. A substantial progress was made by Franz Wethlo (1877 – 1960), who worked at the Berlin university
The historical collection (HAPS) at the TU Dresden owns several cushion pipes from Wethlo in different sizes, modelling male, female, and children’s voices. A team from the TU Dresden repeated Wethlo’s experiments with his original equipment in 2004. Therefore, the cushion pipes were connected to a historical “vocal tract model”. This vocal tract model was actually a stack of wooden plates with holes of different diameters to model the varying cross-sectional area of the vocal tract between the glottis and the lips (Fig. 3). This “configurable” vocal tract model came to the HAPS collections from the Institute of Phonetics in Cologne. The artificial vocal folds were used to excite vocal tract configurations for the vowels /a/, /i/ and /u/, but listening experiments showed that these artificial vowels were rather difficult to discriminate.
Today, there is renewed interest in
Rüdiger Hoffmann & Peter Birkholz
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