VISEME CLASSIFICATIONS OF DUTCH CONSONANTS AND VOWELS

Videotaped lists of meaningless Dutch syllables were presented in quie t to four subject groups, differing with respect to their knowledge of and experience with lipreading (lipreading expertise). Syllables cons isted of all Dutch consonants within three vowel contexts, and of all Dutch vowels within four consonant contexts. Three Speakers pronounced all syllable lists. The aim of the research was (1) to establish vise me classifications of Dutch vowels and consonants; (2) to interpret th e visual-perceptual dimensions underlying this classification and rela te them to acoustic-phonetic parameters; (3) to establish the effect o f lipreading expertise on the classification of visually similar phone mes (visemes). In general, viseme classification proved very constant with different subject groups: Lipreading expertise is not related to viseme recognition. Important visual features in consonant lipreading are lip articulation, degree of oral cavity opening, and place of arti culation, leading to the following viseme classification; /p,b,m/, /f, v,upsilon/, /s,z,integral/, and /t,d,n,j,l,k,x,r,eta,h/. In the acoust ic domain, these features may be related to spectral differences. Vowe l features in lipreading are lip rounding, degree of lip opening, and vowel duration, yielding the following visemes: /i,I,e,epsilon,epsilon i,a,alpha/, /u,y,oe,c/, /o,o/, and /au,oe y/. In the acoustic domain, lip rounding may roughly be related to the second formant, lip openin g to the first formant.