Hearing speech against spatially separate competing speech versus competing noise.

Listeners had the task of following a target speech signal heard against two competitors either located at the same spatial position as the target or displaced symmetrically to locations flanking it. When speech was the competitor, there was a significantly higher separation effect (maintained intelligibility with reduced target sound level), as compared with either steady-state or fluctuating noises. Increasing the extent of spatial separation slightly increased the effect, and a substantial contribution of interaural time differences was observed. When same- and opposite-sex voices were used, a hypothesis that the similarity between target and competing speech would explain the role for spatial separation was partly supported. High- and low-pass filtering showed that both parts of an acoustically similar competing signal contribute to the phenomenon. We conclude that, in parsing the auditory array, attention to spatial cues is heightened when the components of the array are confusable on other acoustic grounds.