Auditory reachability: An affordance approach to the perception of sound source distance

The literature on perception of sound source distance reveals a wide range of listener accuracy. Most experiments have listeners perform unintuitive tasks, using unnatural sounds presented in impoverished acoustic environments. The present experiments implement an affordance paradigm for which listeners judge the ''reachability'' of a natural, live sound source in a familiar acoustic environment. Results reveal that listeners are quite accurate in judging whether the source is reachable and are sensitive to the advantage afforded by two vs. one degree of freedom reaches. Further analyses reveal that when scaled to an intrinsic bodily dimension, judgment differences between listeners disappear, implicating intrinsically scaled specificational information. A follow up experiment explores the potential informational support for these judgments testing the usefulness of head movements and binaural hearing. Results reveal that whereas head movements had no bearing on either judgment accuracy or consistency, binaural information did enhance listener consistency. This could suggest that the allometric relation between interaural distance and arm length might provide a basis for auditory reachability judgments.