Acoustic Discriminability of the Complex Phonation System in !Xóõ

Phonation types, or contrastive voice qualities, are minimally produced using complex movements of the vocal folds, but may additionally involve constriction in the supraglottal and pharyngeal cavities. These complex articulations in turn produce a multidimensional acoustic output that can be modeled in various ways. In this study, I investigate whether the psychoacoustic model of voice by Kreiman et al. (2014) succeeds at distinguishing six phonation types of !Xóõ. Linear discriminant analysis is performed using parameters from the model averaged over the entire vowel as well as for the first and final halves of the vowel. The results indicate very high classification accuracy for all phonation types. Measures averaged over the vowel's entire duration are closely correlated with the discriminant functions, suggesting that they are sufficient for distinguishing even dynamic phonation types. Measures from all classes of parameters are correlated with the linear discriminant functions; in particular, the "strident" vowels, which are harsh in quality, are characterized by their noise, changes in spectral tilt, decrease in voicing amplitude and frequency, and raising of the first formant. Despite the large number of contrasts and the time-varying characteristics of many of the phonation types, the phonation contrasts in !Xóõ remain well differentiated acoustically.