The labial viseme reconsidered: Evidence from production and perception.
Connor Mayer, Jennifer Abel, Adriano Vilela Barbosa, Alexis K. Black, Eric Vatikiotis‐Bateson · The Journal of the Acoustical Society of America · 2011
Previous studies have demonstrated that the labial stops /p,b,m/ may be impossible to discriminate visually, leading to their designation as a single viseme. This perceptual limitation has engendered the belief that there are no visible differences in the production of /p,b,m/, with consequences for research in machine recognition, where production differences below the level of the viseme have been largely ignored. Kinematic studies using high-speed cine, however, have previously documented systematic differences in the production of labial consonants. This study examines the degree to which visual /p,b,m/ are discriminable in production and perception. Two experiments—one designed to measure kinematic orofacial movement using optical flow analysis and one designed to test perceiver discrimination of /p,b,m/—were used to establish the absence/presence of systematic visual differences in bilabial productions, and to replicate the previous perception findings. Results from the optical flow analysis indicate systematic kinematic differences for the peak velocity of the lower face, which corresponds to the release of the bilabial consonant. Significant differences were found in velocity between /m/ and /b/, and between /p/ and /b/, but not between /p/ and /m/. Preliminary results from the perception task suggest discrimination of bilabial consonants is at chance level.