Front Back mirror image reversal errors and left right asymmetry in sound localization

摘要

This research investigated left/right asymmetries in sound localization in sixteen normal-hearing young adults. The study was conducted in a semi-reverberant sound proof chamber that modelled a real-world office environment. The subject was required to identify the direction of a 300-ms auditory stimulus (one-third octave band centred at 0.5 or 4 kHz or broadband noise), randomly emanating from an array of 4 or 8 loudspeakers surrounding him/her, at a distance of 1 m. For the 4-speaker array, loudspeakers were placed either close to the midline (+/- 15 and +/- 165 degrees) or interaural (+/-75 and +/-105 degrees) axes. For the 8- speaker array, two loudspeakers were placed in each spatial quadrant, one at the midline position and the second separated from the first by 15, 30, 45 or 60 degrees. The broadband noise proved easiest to localize and the 0.5 id-It one-third octave band the most difficult. At 0.5 kHz, accuracy in speaker identification was higher on the left than the right. This outcome was largely due to a greater proportion of front/back mirror image reversal errors on the right, particularly for the midline azimuth. A two-coordinate system proposed by Morimoto et al. [1] provided a good fit to the data and confirmed that the difference in accuracy for 0.5 kHz and 4 kHz was due to differences in front/back confusions rather than the perception of azimuth, per se. [References: 28]