title: Modelling of human low frequency sound localization acuity demonstrates dominance of spatial variation of interaural time difference and suggests uniform just-noticeable differences in interaural time difference.
abstract: Sound source localization is critical to animal survival and for identification of auditory objects. We investigated the acuity with which humans localize low frequency, pure tone sounds using timing differences between the ears. These small differences in time, known as interaural time differences or ITDs, are identified in a manner that allows localization acuity of around 1° at the midline. Acuity, a relative measure of localization ability, displays a non-linear variation as sound sources are positioned more laterally. All species studied localize sounds best at the midline and progressively worse as the sound is located out towards the side. To understand why sound localization displays this variation with azimuthal angle, we took a first-principles, systemic, analytical approach to model localization acuity. We calculated how ITDs vary with sound frequency, head size and sound source location for humans. This allowed us to model ITD variation for previously published experimental acuity data and determine the distribution of just-noticeable differences in ITD. Our results suggest that the best-fit model is one whereby just-noticeable differences in ITDs are identified with uniform or close to uniform sensitivity across the physiological range. We discuss how our results have several implications for neural ITD processing in different species as well as development of the auditory system.
authors.affiliation: Department of Cell and Developmental Biology, University College London, London, United Kingdom ; Centre for Mathematics, Physics and Engineering in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, United Kingdom.
authors.forename: Rosanna C G
authors.initials: RC
authors.lastname: Smith
authors.affiliation: Department of Cell and Developmental Biology, University College London, London, United Kingdom.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Price
mesh_terms: D006801:Humans; D008960:Models, Psychological; D013016:Sound; D013017:Sound Localization / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D013045:Species Specificity; D013998:Time Perception / Q000502:physiology*