Vertical sound localization in left, median and right lateral planes

Abstract

A few studies have reported better auditory localization under binaural listening for sounds presented from the left side of midline compared to the right. That asymmetry was attributed to a superior ability to resolve front/back confusions in the left hemifield. This research further investigated asymmetric effects in an experiment assessing vertical localization in three lateral planes perpendicular to the interaural axis (median, left and right). Eleven sources spaced at 18-deg intervals were arrayed around the upper half of the cone-of-confusion intersection in each plane. Subjects (15 males, 9 females) were required to identify the direction of incidence of a 250-ms band-limited white noise stimulus (250-8000 Hz). Statistical analyses performed on the proportion of correct responses and on three different angular error measures did not uncover any significant effect in performance for sources on the left versus right side of subjects. However, significant gender differences favoring male subjects were found for the variable and total error measures. This finding may be a purely physical effect due to the smaller size of female ears on average or related to cognitive effects. Results must be viewed in light of the wide distribution of response patterns from subject to subject; while most responded symmetrically and over the entire localization array, some had distinctive asymmetrical behaviors and/or systematic response biases in specific sectors of the localization array.