Measuring and modeling speech intelligibility in real and loudspeaker-based virtual sound environments.

Loudspeaker-based virtual sound environments provide a valuable tool for studying speech perception in realistic, but controllable and reproducible acoustic environments. The evaluation of different loudspeaker reproduction methods with respect to perceptual measures has been rather limited. This study focused on comparing speech intelligibility as measured in a reverberant reference room with virtual versions of that room. Two reproduction methods were based on room acoustic simulations, presented either using mixed-order ambisonics or nearest loudspeaker mapping playback. The third method utilized impulse responses measured with a spherical microphone array and mixed-order ambisonics. Three factors that affect speech intelligibility were varied: reverberation, the spatial configuration and the type of the interferers (speech or noise). Two interferers were placed either colocated with the target, or were symmetrically or asymmetrically separated. The results showed differences between the reference room and the simulation-based reproductions when the target and the interferers were spatially separated but not when they were colocated. The reproduction utilizing the microphone array was most similar to the reference room in terms of measured speech intelligibility. Differences in speech intelligibility could be accounted for using a binaural speech intelligibility model which considers better-ear signal-to-noise ratio differences and binaural unmasking effects. Thus, auditory modeling might be a fast and efficient way to evaluate virtual sound environments.