The role of visual cues indicating onset times of target speech syllables in release from informational or energetic masking

This study examined the effect of visual cues that provide the timing information of syllables in nonsense target sentences on the recognition of target speech against either a speech-spectrum noise masker or a two-talker masker. When the target sentences with normally regular rhythm were used (Experiment 1), visual cues indicating the onset times of the target-sentence syllables did not significantly improve target-speech recognition against either the speech-spectrum noise masker or the two-talker masker. On the other hand, recognition of the last (third) keyword in these normal rhythmic sentences was significantly better than that of the first keyword against the two-talker masker, but not the noise masker. This word-position-related speech-recognition improvement indicates a beneficial role of regular speech rhythm in release from informational masking due to the temporal prediction of target-sentence syllables. When artificially irregular rhythms were introduced into target sentences (Experiment 2), visual cues indicating syllable onset times significantly improved target-speech recognition against both types of masker. Moreover, the visual-cue-induced improvement in speech recognition against the two-talker masker was significantly larger than that against the speech-spectrum noise masker. The results of this study suggested that visual cues indicating target-syllable timing information improve target-speech recognition against competing maskers only when the temporal rhythmic regularity of target speech sentences is reduced.