Effect of speed difference between time-expanded speech and moving image of talker’s face on word intelligibility

Abstract

This study investigated effects of asynchrony between speech signal and moving image of talker’s face induced by time-expansion of the speech signal on speech intelligibility. Word intelligibility test was performed to younger listeners. Japanese 4-mora words were uttered by a female speaker. Each word was processed with STRAIGHT software to expand the speech signal by from 0 to 400 ms. These signals were combined with moving image of talker’s face which was kept at original speed. This test was performed under three conditions: visual-only, auditory-only, and auditory-visual (AV) condition. Results showed that intelligibility scores under AV condition were statistically higher than those under auditory-only condition even when the speech signal was expanded by 400 ms. These results suggest that moving image of talker’s face is effective to enhance speech intelligibility if the lag between the speech signal and moving image of talker’s face does not exceed 400 ms.