Quantifying the effects of room acoustics on speech intelligibility in very low signal-to-noise ratio environments

Abstract

The intelligibility of speech transmitted from closed offices to adjacent spaces is strongly affected by the signal-to-noise ratio at the receiver position and the acoustical characteristics of the spaces involved. Previous studies have suggested that the effect of room acoustics on speech intelligibility in closed offices and rooms is negligible and can be ignored (as with intelligibility quantifiers such as the articulation index). The purpose of this study is to show that in conditions of very low signal-to-noise (i.e., when high speech privacy is a primary concern), the influence of room acoustics rises dramatically. To this end, multiple subjects were given tests of speech intelligibility in simulated sound fields. Speech samples were presented to subjects with seven levels of signal-to-noise and four different reverberation times. The results from these tests show that as reverberation time increases, speech intelligibility decreases much more sharply for very low (−8 dB) signal-to-noise situations than in higher (+10 dB) signal-to-noise situations. This suggests an important relationship between room acoustics and speech privacy/security.