Some spatial and temporal effects on the speech privacy of meeting rooms

This paper reports on initial experiments concerning how key spatial and temporal effects in rooms influence the speech privacy provided by enclosed rooms. The first part of the work demonstrates that for the same signal-to-noise ratio, the intelligibility of speech and the threshold of intelligibility are significantly different for transmission between real rooms than in the previous results in approximately free-field conditions [B. N. Gover and J. S. Bradley, J. Acoust. Soc. Am. 116, 3480-3490 (2004)]. The second part investigates the influence of aspects of the spatial and temporal components of sound fields in typical rooms, to explain these differences for transmission between real rooms. These components included the separate effects of early-arriving and later-arriving reflected speech sounds. They also included the effects of spatially separated speech and noise sources as well as more diffuse noise representative of typical meeting rooms. In realistic combinations these effects are of practical importance and can change privacy criteria by 5 dB or more. Ignoring them could lead to costly over-design of the sound insulation required to achieve adequate speech privacy.