Two-dimensional sound localization by human listeners

Abstract

This study measured the ability of subjects to localize broadband sound sources that varied in both horizontal and vertical location. Brief (150 ms) sounds were presented in a free field, and subjects reported the apparent stimulus location by turning to face the sound source; head orientation was measured electromagnetically. Localization of continuous sounds also was tested to estimate errors in the motor act of orienting with the head. Localization performance was excellent for brief sounds presented in front of the subject. The smallest errors, averaged across subjects, were about 2 degrees and 3.5 degrees in the horizontal and vertical dimensions, respectively. The sizes of errors increased, for more peripheral stimulus locations, to maxima of about 20 degrees. Localization performance was better in the horizontal than in the vertical dimension for stimuli located on or near the frontal midline, but the opposite was true for most stimuli located further peripheral. Front/back confusions occurred in 6% of trials; the characteristics of those responses suggest that subjects derived horizontal localization information principally from interaural difference cues. The generally high level of performance obtained with the head orientation technique argues for its utility in continuing studies of sound localization.

Stretched and upside-down maps of auditory space in the optic tectum of blind-reared owls; acoustic basis and behavioral correlates

“…(It should be remembered here that, with the technique of measuring sound localization we used, both inconsistency in localization and systematic errors associated with specific regions of space can contribute to response variance.) Even with this degradation in performance, sound localization by blind-reared owls is good compared to the normal localization abilities of most other species, with the notable exception of humans (Makous and Middlebrooks, 1990). Thus, nonvisual sources of information can establish a reasonably good perception of auditory space without vision.…”

Specialization for Sound Localization in Fields A1, DZ, and PAF of Cat Auditory Cortex

“…These observations suggest that PAF might have a principal role in sound localization. A difficulty with that argument is that populations of PAF neurons show their greatest location signaling accuracy for lateral regions of space, whereas psychophysical localization accuracy in cats (May and Huang, 1996;Tollin et al, 2005) and humans (e.g., Makous and Middlebrooks, 1990;Carlile et al, 1997) is greatest around the frontal midline. It might be that PAF scans regions that are remote from frontal attention, cooperating with another cortical field, such as DZ, to provide highacuity localization near the midline.…”

Can measures of sound localization acuity be related to the precision of absolute location estimates?

“…(1) (Hartmann and Rakerd, 1989;Makous and Middlebrooks, 1990;Recanzone et al, 1998). Such comparisons could theoretically be valid if the assumptions typical to analyses of 2AFC tasks are satisfied, if data collected from absolute tasks accurately represent a subject's perceptual abilities, and that any effects arising from the disparities between tasks are inconsequential.…”

“…Unambiguous estimates of both accuracy and precision can be obtained from absolute paradigms but only a single measure of acuity, the MAA, is computed from relative tasks. It has frequently been inferred (e.g., Perrott, 1984;Perrott et al, 1987;Heffner and Heffner, 1992;Grantham et al, 2003), and occasionally directly suggested (Hartmann and Rakerd, 1989;Makous and Middlebrooks, 1990;Recanzone et al, 1998), that the MAA is specifically related to the precision of absolute sound localization estimates. In other words, the size of the MAA is singularly dependent upon the resolution with which a subject's auditory system computes directional cues, and therefore it conveys the consistency with which that observer could report the apparent location of sound sources in an absolute task.…”

“…Despite a general correspondence between absolute and relative psychophysical measures (Makous and Middlebrooks, 1990;Recanzone et al, 1998), there are several examples of severe departures between them. For example, humans have repeatedly been measured to have MAAs near 1° for both low-and high-frequency pure tone stimuli (Mills, 1958;Perrott, 1969;Blauert, 1997), yet subjects who are required to actually indicate the spatial location of such stimuli often display large variability and poor accuracy in their responses (Stevens and Newman, 1936;Middlebrooks, 1992).…”