Accuracy versus choice response time in sound localization

An experiment was conducted to further explore sound localization for frontal sound incidence. The question of interest was whether two response measures, accuracy in loudspeaker identification and choice response time would be differentially affected by variation in three parameters. These were the number Of loudspeakers (three, five and seven), the separation between speakers (15 degrees versus 30 degrees), and stimulus frequency (500 versus 4000 Hz). Twelve normal-hearing subjects were tested in a semi-reverberant room that modelled real-world listening. Each was presented 12 blocks of listening trials, across ,which the 12 conditions were presented in random order. A block comprised 20 random presentations of a 300-ms one-third octave noise band from each speaker. Subjects responded using a set of microswitches in the same configuration as the loudspeaker array. Accuracy decreased as the number of speakers increased and their separation decreased. Response time increased with number but was unaffected by separation. The effect of frequency was relatively small. A two-stage conceptual model, consisting of sensory encoding and non-sensory decision-making, provided a reasonable framework for the results. (C) 1997 Elsevier Science Ltd.