A dissociation between speech understanding and perceived reverberation

As direct-to-reverberant energy ratio (DRR) decreases or decay time increases, speech intelligibility tends to decrease for both normal-hearing and hearing-impaired listeners. Given this relationship, it is easy to assume that perceived reverberation (reverberance) would act as an intermediary-as physical reverberation increases, so does reverberance, and speech intelligibility decreases as a result. This assumption has not been tested explicitly. Two experiments were conducted to test this hypothesis. In Experiment 1, listeners performed a magnitude estimation task, reporting reverberance for speech stimuli that were convolved with impulse responses whose reverberant properties were manipulated. Listeners reported a decrease in reverberance when the DRR was increased at both ears (Natural Room condition), but not when it was increased at only the ear nearest the source (Hybrid condition). In Experiment 2, listeners performed a speech intelligibility task wherein noise-masked speech was convolved with a subset of the impulse responses from Experiment 1. As predicted by the speech transmission index (STI), speech intelligibility was good in cases where at least one ear received non-reverberant speech, including the Hybrid listening condition in Experiment 1. Thus, the Hybrid listening condition resulted simultaneously in high reverberance (Exp. 1) and high speech intelligibility (Exp. 2), demonstrating that reverberance and speech intelligibility can be dissociated.