A laboratory study for assessing speech privacy in a simulated open-plan office

The aim of this study is to assess speech privacy in open-plan office using two recently introduced single-number quantities: the spatial decay rate of speech, DL2,S [dB], and the A-weighted sound pressure level of speech at a distance of 4m, L-p,L-A,L-S,L-4m [dB]. Open-plan offices were modeled using a DL2,S of 4, 8, and 12dB, and L-p,L-A,L-S,L-4m was changed in three steps, from 43 to 57dB. Auditory experiments were conducted at three locations with source-receiver distances of 8, 16, and 24m, while background noise level was fixed at 30dBA. A total of 20 subjects were asked to rate the speech intelligibility and listening difficulty of 240 Korean sentences in such surroundings. The speech intelligibility scores were not affected by DL2,S or L-p,L-A,L-S,L-4m at a source-receiver distance of 8m; however, listening difficulty ratings were significantly changed with increasing DL2,S and L-p,L-A,L-S,L-4m values. At other locations, the influences of DL2,S and L-p,L-A,L-S,L-4m on speech intelligibility and listening difficulty ratings were significant. It was also found that the speech intelligibility scores and listening difficulty ratings were considerably changed with increasing the distraction distance (r(D)). Furthermore, listening difficulty is more sensitive to variations in DL2,S and L-p,L-A,L-S,L-4m than intelligibility scores for sound fields with high speech transmission performances.