The bigger the better and the more the merrier? Realistic office reverberation levels abolish cognitive distraction by multiple-voice speech

Background speech is consistently rated as the most objectionable noise in open-plan offices. There is ample evidence that acoustic variation in the speech is a key determinant of its disruption of cognitive performance. Theoretically, any means of attenuating sound variability such as increasing room reverberation should help counter the negative impact of irrelevant speech. To date, such benefits have been reported only with reverberation times uncharacteristic of office environments. Based on the observation that multiple voices are less disruptive than a single voice, we sought to test the joint impact of number of voices and reverberation on the disruptive effects of speech. The effects on a (visually-presented) short-term serial recall task of adding realistic reverberation times (0.4 or 1 s) to irrelevant speech emanating from either 3 or 15 superimposed voices was compared to a quiet control condition. Disruption diminished with both an increase in number of voices and with increasing reverberation and disappeared in the 15-voice+long-reverberation condition, suggesting that realistic room reverberation levels may ameliorate the damaging effects of background speech in relatively large multiple-occupancy offices.