phonations, we need in turn to better understand the information provided by EGG signals: how do EGG pulse landmarks and EGG pulse shapes relate to each other and to the perception of phonation? In this connection, we will follow Mooshammer (2010) in applying Functional Data Analysis to EGG pulse shapes, and we will relate the components of the shapes obtained in this way to other EGG measures, as well as to perception. Thus our secondary goal is to contribute to the understanding of EGG measures of phonation type. II. BACKGROUND A. Languages Southern Yi, Bo, and Hani are Yi (also called Loloish) languages in the Tibeto-Burman family of the Sino-Tibetan phylum. The name “Yi” refers to both the whole Yi (Loloish) branch of languages and the Yi language, because it has the largest population in this language family branch. The Yi language branch includes perhaps fifty languages, geographically distributed in Yunnan, Sichuan and Guizhou provinces of China, and spoken by more than six million people (Ethnologue, 2012). Yi languages typically have a CV syllable structure, a seven-vowel system, a three-tone system (low, mid and high, noted as 21, 33 and 55), and two phonation registers: tense vs. lax. B. Production of phonation types The four types of non-modal phonations referred to in the previous section (breathy, creaky, lax and tense - ref. Figure 1) are defined with respect to modal phonation. In modal phonation, the vocal folds vibrate along their entire lengths, often with full closure,
and their vibration is periodic. In breathy phonation, tension is low, the overall glottal aperture is increased, the closure of the folds is incomplete and of short duration, the vibratory pulse is symmetrical in shape, and glottal airflow is high, leading to a strong first harmonic and audible frication noise (Laver, 1980; Pennington, 2005; Gobl and Ni Chasaide, 2012). Lax phonation is supposed to have a similar (“slack”) glottal configuration, but less extreme. In contrast, tense (or “stiff” or “pressed”) phonation is characterized by increased adductive tension and medial compression, so that the glottal aperture is reduced and only the ligamental part of the vocal folds vibrates. The closure of the folds is complete and abrupt, and of longer duration, and the pulse shape is skewed, increasing the energy in the higher frequencies. Glottal airflow is low, leading to a weaker first harmonic (Gobl and Ni Chasaide, 2012). Tense phonation may also involve a higher degree of tension in the entire vocal tract, affecting the respiratory system as well as the supralaryngeal tract. Creaky voice is essentially similar, but due to greater tension and possible incursion of the ventricular folds, vibration is irregular (Childers et al., 1990; Gobl and Ni Chasaide, 2012). These descriptions generally suggest that tense and lax phonations are produced quite similarly to creaky and breathy phonations, respectively; however, Figure 1 above suggests that acoustically, they are much more similar to modal phonation, and to each other, than to these extreme non-modal phonations. C. Previous studies of Tibeto-Burman phonation types The acoustic correlates associated with tense vs. lax contrasts in Tibeto-Burman languages have received some attention in the literature. Several studies have identified
represent it. FDA on just these stimuli showed that the first two PCA components for this subset are very much like those in Figure 5 and account for similar variance (74.4%), confirming that the EGG pulse shapes for tense vs. lax phonation are consistent; correlation analyses between the factors and the principle component scores again show that PC1 is dominated by phonation, while PC2 is related to gender, PC3 has both phonation and gender effects, and PC4 is mostly related to tone, and to f0. Vowel quality does not affect glottal pulse shapes. Correlation coefficients between principle component scores and EGG parameters show that, just as was found for the full dataset (results for the full dataset are seen in Table III), the phonation-related pulse shape components (PC1 and PC3) are best correlated with the CQ measure. SQ and closing duration are also very important EGG parameters that can capture aspects of the phonation-related pulse shapes. F0 shows a strong correlation (r=-0.6) with opening duration. C. Production-perception relations Given these analyses of the EGG signals of the 48 test stimuli, we can now calculate the correlations of the mean perceptual accuracy scores from Kuang (2011) with the different characterizations of the EGG pulses, and with the acoustic measures. Considering the FDA analysis, significant correlations with perception accuracy are found only for PC1 (r=0.49, p<0.001) and, more weakly, for PC3 (r=0.13, p<.05). Specifically, as listeners had to attend to the phonation contrast in order to classify the stimuli, the identification accuracy rates are only highly correlated to PC1, while PC2, a shape component related to gender, is successfully factored out by listeners. Although
thesis, University of California, Los Angeles. Kuang, J., and Keating, P. (2012). “Glottal articulations of phonation contrasts and their acoustic and perceptual consequences,” UCLA Working Papers in Phonetics 111, 123–161. Kuang, J. (2013). “Phonation in tonal contrasts,” Ph.D. thesis, University of California, Los Angeles. Ladefoged, P. (1964). A phonetic study of West African languages (Cambridge University Press, Cambridge), pp.1–74. Ladefoged, P. (1971). Preliminaries to linguistic phonetics (University of Chicago Press, Chicago), pp.1–123. Larson, K. K., Ramig, L. O., and Scherer, R. C. (1994). “Acoustic and glottographic voice analysis during drug-related fluctuations in Parkinson’s disease,” J. Med. Speech Lang. Pathol. 2, 227–239. Laver, J. (1980). The Phonetic Description of Voice Quality (Cambridge University Press, Cambridge), pp.1–186. Lee, S., Byrd, D., and Krivokapic, J. (2006). “Functional data analysis of prosodic effects on articulatory timing,” J. Acoust. Soc. Am. 119, 1666–1671. Lowell, S.Y., and Story, B.H. (2006). “Simulated effects of cricothyroid and thyroarytenoid muscle activation on adult-male vocal fold vibration,” J. Acoust. Soc. Am. 120, 386–397. Maddieson, I., and Ladefoged, P. (1985). ““Tense” and “lax” in four minority languages of China,” J. Phonetics 13, 433–454. Maddieson, I., and Hess, S. (1986). ““Tense” and “Lax” revisited: more on phonation