The effect of room acoustics on the measured speech privacy in two typical European open plan offices

摘要

The reverberation time and the background noise level are often used as the most important design parameters in European open plan offices to achieve a comfortable acoustic climate and to control speech intelligibility. Good speech intelligibility is desired for people working together, but bad speech intelligibility is desired between independent working groups. The latter situation is also referred to as speech privacy. To investigate speech privacy, acoustical parameters like STI and the SII can be used. Both parameters rely on the use of two types of weighted signal to noise ratios to determine the speech intelligibility, taking into account the speech level, background noise level and room acoustics. The influence of room acoustics is translated to an apparent signal to noise ratio by the use of the Modulation Transfer Function (SNR1). Besides that, room acoustics influences the received speech level, which together with the background noise results in another signal to noise ratio (SNR2). To investigate the influence of both types of SNR on the speech privacy, the STI was measured of two typical European open plan offices for the situations with and without SNR1 and with and without SNR2. The results show that the difference between the STI with and without SNR1 is within the estimated JND of 0.1 between independent working groups. The difference between with and without SNR2 is far beyond the estimated JND.