A statistical study of tongue muscle EMG and vowel formant frequencies.

Abstract

Toward designing a realistic model of the vocal tract to explain transformational processes from motor to acoustic patterns, statistical relationships between activities of several articulatory muscles and vowel formant frequencies were examined. The EMG and acoustic data of Haskins Laboratories obtained during repetitions of /schwa pvp/ word utterances were used to compare the token-to-token variabilities of EMG signals for vowel segments and of vowels formants. A large variability of EMG signals observed for each tongue muscle during repetitions of the identical utterances seems to be compensated for by other muscles or jaw positions to realize small variabilities of formant frequencies. The extrinsic tongue muscles showed various degrees of correlations with vowel formants. The anterior and posterior genioglossus muscles had a high correlation with F1 and F2 for /i/, and they also showed a positive correlation with F0. The hyoglossus and the anterior genioglossus showed a relatively high correlation with F1 and F2 for /a/, even when jaw position data were excluded, but not significant correlation with F0. The observations from further analyses will be discussed in terms of vocal tract length adjustment. [Work supported in part by an NIH grant to Haskins Laboratories.]