Acuity of Sound Localisation: A Topography of Auditory Space. I. Normal Hearing Conditions

Abstract

Eight subjects were required to localise a sound source (white noise through a speaker) which varied in position on both sides of the head over a range of elevations (-40 degrees to +40 degrees) and azimuths (0 degree to 180 degrees) at 10 degrees intervals. The perceived position of the source was indicated by pointing a special gun. Depression of the trigger activated a photographic system which recorded two views of the subject, the sound source, and the gun. The absolute and algebraic, azimuth and elevation errors were measured for all subjects at each position of the source. The variability of azimuth and elevation error was also computed. In a second experiment, four of the same subjects performed the same task but in this case visually located the sources. This experiment provided an estimate of inherent motor error in the pointing task. No differences in localisation acuity between sides were found, but there were significant differences between front and back regions. Azimuth and elevation error were well matched and low in the front. However, azimuth error increased in the regions behind the head, particularly for azimuth positions 120 degrees to 160 degrees. Larger increases were found for positions in the upper elevations of this region. Elevation error also increased in the upper elevations behind the head. A comparison of the auditory and visual data indicates that this pattern of error is not due to motor factors. The results are discussed in relation to the structural characteristics of the pinnae and modifications that they impose on incoming sound energy.

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

“…The cats in the present study localized sounds via gaze shifts, which requires coordination between the neural representation of auditory space and the motor systems controlling eye and head movements . Localization errors may therefore result from any of several causes, including intrinsic properties of the auditory system (Rayleigh, 1907;Stevens and Newman, 1936;Yin, 2002), ambiguity in the encoding of spatial cues (Wallach, 1939;Oldfield and Parker, 1984), a mismatch between the auditory and visual systems (Knudsen and Knudsen, 1985;Zwiers et al, 2003) and/or limitations of the oculomotor system. While it is possible that biases in absolute location estimates largely result from motor effects, it seems at least equally plausible that the computation and representation of acoustic spatial cues are inherently imperfect.…”

WIRE 3 : Driving Around the Information Super-Highway

“…Our approach for conveying the position in the document exploits the listener's ability to accurately identify sound sources along the x-axis. Results offered by Oldfield et al [27] indicate that humans can identify the location of a sound source along the x-axis to within nine degrees.…”

Position Identification by Actively Localizing Spacial Sound Beacons

“…In general, the ATD between two microphones restricts a sound source to the surface of a rotated hyperbola. It can be approximated by the surface of a cone, known as the "cone of confusion" in psychoacoustic research [9], [10].…”