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

This research investigated left/right asymmetries in sound localization in sixteen normal-hearing young adults. The study was conducted in a semi-reve rberant sound proof chamber that modelled a real-world office environment. The subject was required to identify the direction of a 300-ms auditory sti mulus (one-third octave band centred at 0.5 or 4 kHz or broadband noise), r andomly 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 ei ther 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 th e 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 accu racy for 0.5 kHz and 4 kHz was due to differences in front/back confusions rather than the perception of azimuth, per se.