The Effect of Auditory Spatial Layout in a Divided Attention Task

The effect of spatial separation on the ability of listeners to report keywords from two simultaneous talkers was examined. The talkers were presented with equal intensity at a clearly audible level, and were designed to have little spectral overlap in order to reduce energetic interference. The two talkers were presented in a virtual auditory environment with various angular separations around references of -45o, 0o, or 45o azimuth. In Experiment 1, the virtual space was created using head-related transfer functions (HRTFs) which contained natural energy variations as a function of location. In Experiment 2, these energy variations were removed and the virtual space was created using only interaural time differences (ITDs). Overall, performance did not vary dramatically but depended on spatial separation, reference direction, and type of simulation. Around the 0o reference azimuth, performance in the HRTF condition tended to first increase and then decrease with increasing separation. This effect was greatly reduced in the ITD condition and thus appears to be related primarily to energy variations at the two ears. For sources around the ± 45o reference azimuths, there was an advantage to separating the two sources in both HRTF and ITD conditions, suggesting that perceived spatial separation is advantageous in a divided attention task, at least for lateral sources.