Effects of type of early reflection, clarity of speech, reverberation and diffuse noise on the spatial perception of a speech source and its intelligibility

Changing the balance between the early and late reflections in the impulse response affects the clarity of speech, and also the spatial perception of the sound source is affected when the direction of the early reflections is manipulated. While the effect of noise on early reflections has long been investigated in speech intelligibility studies, it is unclear whether and how the spatial characteristics of the source are altered by noise, and whether this would influence speech intelligibility in any way. The aim of the present work was to analyze the spatial perception of a speech source in noise and its relationship, if any, with speech intelligibility. Impulse responses with specular or scattered early reflections and two different reverberant tails were used to create sound fields with controlled clarity and reverberation. It emerged that noise affects spatial cues compared to the reverberation-only (quiet) condition; ratings are consequently changed, and most percepts are distorted. Speech intelligibility is also sensitive to changes in acoustic variables and the type of reflection, but the direct association between spatial percepts and speech intelligibility is weak.