Effects of auditory masking on lip movements during speech

This study describes the effects of unpredictably presented masking noise on selected parameters of lip movement during speech. Four normal subjects produced a simple speech utterance while vertical displacements of the upper and lower lips were transduced and recorded. During selected productions a masking noise was presented dichotically at one of two distinct phases of lip movement. Analysis of the resulting data revealed the following for all subjects: (1) significant changes in the duration, displacement, and velocity of lip movement caused by masking and (2) significant reductions in the velocity of lip movement occurring approximately 50 msec after the onset of the masker. Possible explanations of these and certain speaker-dependent effects are discussed.