Visual Speech Perception, Optical Phonetics, and Synthetic Speech

The information in optical speech signals is phonetically impoverished compared to the information in acoustic speech signals that are presented under good listening conditions. But high lipreading scores among prelingually deaf adults inform us that optical speech signals are in fact rich in phonetic information. Hearing lipreaders are not as accurate as deaf lipreaders, but they too demonstrate perception of detailed optical phonetic information. This chapter briefly sketches the historical context of and impediments to knowledge about optical phonetics and visual speech perception (lipreading). The authors review findings on deaf and hearing lipreaders. Then we review recent results on relationships between optical speech signals and visual speech perception. We extend the discussion of these relationships to the development of visual speech synthesis. We advocate for a close relationship between visual speech perception research and development of synthetic visible speech.