The effects of speechreading training on viseme categories for vowels

Abstract

The status of visemes, groups of visually confusable speech sounds, for American English vowels has been disputed for some time. While some researchers claim that vowels are visually distinguishable, others claim that some vowels are visually confusable and comprise viseme categories. Data from our study on speechreading words and sentences were examined for evidence of vowel visemes [C. Richie and D. Kewley-Port, J. Acoust. Soc. Am. 117, 2570 (2005)]. Normal-hearing listeners were tested in auditory-visual conditions in masking noise designed to simulate a hearing loss. They were trained on speechreading tasks emphasizing vowels, consonants, or vowels and consonants combined. Pre- and post-training speechreading tests included identification of 10 vowels in CVC context. Pre-training data (vowel-identification confusion matrices) were used to determine whether vowel visemes exist for untrained speechreaders. Post-training results were examined to determine whether the number of vowel response categories increased and whether the number of vowel identification errors decreased, for trained versus untrained participants. The impact of these training programs on speechreading performance is discussed in terms of vowel visemes. [Work supported by NIHDCD02229.]