A single reflective surface reveals contextual cue-weighting in spatial hearing

Prominent among the factors supporting accurate sound localizatoin in reverberant scenes is the dominance of sound onsets, which carry binaural cues matching the direct sound rather than its echoes. Aspects of onset dominance can be demonstrated synthetically via localization of paired sounds separated by a brief delay (the “precedence effect”)–a rather extreme simplification of reverberation but a useful one for dissecting the roles of single reflections. In 1985, Brad Rakerd and Bill Hartmann published a precedence-like study [JASA 78(2), 524–533] using actual acoustic reflections induced by a single reflective surface positioned within an otherwise-anechoic space. Figure 3 of that paper shows that the effects on localization depend in a complex way on the direction and proximity of the sound source and its reflections. The impacts on binaural acoustic cues are similarly complex. Localization could be predicted by combinations of these cues only if each cue was weighted by its plausibility (i.e., likelihood given the sensory context). With this 1985 study, Rakerd and Hartmann, thus, revealed a second critical factor for accurate spatial hearing in reverberation: the context-dependent weighting of multiple imperfect sensory cues.