Noise unmasks the masking effect of reverberation on early reflections in the intelligibility of speech

Changing the ratio between early and late reflections affects the clarity of speech and music and modulates the spatial impression; this latter effect typically happens when the direction of arrival of reflections is varied too. In this mechanism both the overall amount of energy and the correlation at the ears play a role, the latter being crucial for spatial impressions. When noise is added on speech, it is unclear whether and how the spatial characteristics of the source are altered, nor it is clear if this would affect speech intelligibility. In this work impulse responses with specular or diffuse early reflections and two different reverberant tails are used to create virtual sound fields with control of clarity and reverberation. It is shown that in some cases the presence of noise restores spatial percepts of the speech source that are unavailable in the reverberation-only (quiet) conditions. These cues are associated with an improvement in speech intelligibility.