Acoustical prerequisites for visual hearing

The McGurk effect shows in an obvious manner that visual information from a speaker’s articulatory movements influences the auditory perception. The present study concerns the robustness of such speech specific audiovisual integration. What are the acoustical prerequisites for audiovisual integration to occur in speech perception? Auditory, visual and audiovisual syllables (phonated and whispered) were presented to 23 perceivers. In some of the stimuli, the auditory signal was exchanged for a schwa syllable, a dynamic source signal and a constant source signal. The results show that dynamic spectral information from a source signal suffice as auditory input for speech specific audiovisual integration to occur. The results also confirm that type (and absence) of lip rounding are strong visual cues