Speech recognition in reverberation and background chatter

The subjective impression of acoustical comfort, as shown by previous surveys of restaurant patrons, can be achieved within a narrow range of reverberation time. These surveys also indicated that acoustical comfort is relatively unrelated to the level of background noise. In order to more fully understand the relative effects of reverberation time and noise levels, an experiment was conducted by undergraduate architecture students for speech intelligibility, not acoustical comfort, in a test space where reverberation times and levels of background chatter could be varied. The resulting data suggests that there is a threshold level of reverberation time for speech intelligibility when signal-to-noise ratios are very low, and even negative in value. This finding has consequences for the acoustical design of restaurants where the sounds of social activity are welcomed, but where background chatter should not overwhelm the ability to discern and understand nearby speech.