Roles of frequency information and spatial information in auditory search

Effects of attention on auditory search process were examined with five spatially distributed loudspeakers, each of which radiated a component sound (either a pure tone or a 1/12-octave NBN). The stimulus consisted of five component sounds with different (center) frequencies. The listener’s task was to judge whether or not a target sound was included in the distractors as quickly as possible while minimizing errors [N. Asemi et al., Acta Acustica 89, 346–354 (2003)]. The following three conditions were examined: (1) a control condition with no cue sound; (2) a condition with a preceding cue sound indicating the target sound location; and (3) a probe-signal condition in which 1/8 of the cue sounds provided inconsistent information of frequency and location (probes) while the remainder provided consistent information (primaries). The resultant response times for probes were generally longer than those for primaries. Furthermore, attention windows were observed in both frequency and spatial domains. The effect of the disparities between the cue and target was larger when both the frequency and location differed than when only one of them differed. This result also means that the detection performance becomes better if attention is directed with certain information related to the targets.