Academic journal article Human Factors

Aurally Aided Visual Search in Three-Dimensional Space

Academic journal article Human Factors

Aurally Aided Visual Search in Three-Dimensional Space

Article excerpt

We conducted an experiment to evaluate the effectiveness of spatial audio displays on target acquisition performance. Participants performed a visual search task with and without the aid of a spatial audio display. Potential target locations ranged between plus and minus 180[degrees] in azimuth and from -70[degrees] to +90[degrees] in elevation. Independent variables included the number of visual distractors present (1, 5, 10, 25, 50) and the spatial audio condition (no spatial audio, free-field spatial audio, virtual spatial audio). Results indicated that both free-field and virtual audio cues engendered a significant decrease in search times. Potential applications of this research include the design of spatial audio displays for aircraft cockpits and ground combat vehicles.

INTRODUCTION

Many researchers have investigated the utility of three-dimensional (3D) auditory displays for reducing the workload associated with an overloaded visual channel and for enhancing the detection and identification of visual targets (Flanagan, McAnally, Martin, Meehan, & Oldfield, 1998; Nelson et al., 1998; Perrott, Cisneros, McKinley, & D'Angelo, 1996). Advances in digital signal-processing technology and the development of electromagnetic position trackers have enabled the construction of small, relatively inexpensive spatial audio displays that can be used to aid in visual target acquisition in aircraft cockpits, ground combat vehicles, and training simulators. Recent investigations have demonstrated the utility of spatialized audio cueing for some aircraft applications (Bronkhorst, Veltman, & van Breda, 1996; McKinley & Ericson, 1997). One approach to quantifying the performance advantage afforded by the use of spatial audio displays is to investigate the reduction in search times obtained when such displa ys are used in a target acquisition task. This can be accomplished using the aurally aided visual search paradigm developed by Perrott, Saberi, Brown, and Strybel (1990).

In a classical visual search task, a participant looks for a target stimulus among an array of nontarget stimuli, or distractors. In the usual paradigm, the participant reports either the presence or absence of the target, and his or her reaction time (RT) is recorded. The relationship between RT and the number of distractors is generally linear, with RT either increasing with set size or remaining approximately constant independent of the number of nontarget elements in the field. The former case is generally interpreted as involving some limited-capacity process, in which the observer must direct his or her attention to small sections of the visual field sequentially, and is hence referred to as a serial search. Conversely, searches for which reaction times do not vary with the number of distractors are presumed to involve some "preattentive" or parallel process and are hence termed parallel searches (Treisman & Gelade, 1980; Wolfe, Cave, & Franzel, 1989).

Perrott and his colleagues have investigated the effect of the addition of an audio cue colocated with the visual target on visual search times (Perrott, et al., 1990, 1996; Perrott, Sadralodabai, Saberi, & Strybel, 1991). In one experiment (Perrott et al., 1991) participants searched for a visual target among an array of multiple distractors presented in the central visual field with and without spatial audio cueing. The results of this study indicated that the addition of a spatial audio cue provides a significant reduction in RT even for targets within a few degrees of the fovea.

More recently, Perrott et al. (1996) investigated the trivial case (i.e., one target, zero distractors) of an aurally aided visual search task in which the visual field was less restricted. In this study the target was presented on the interior surface of a geodesic sphere to an observer seated at the center. It was observed that the addition of a spatially correlated audio cue provided a significant reduction in target acquisition times - several hundred ms for targets in the rear hemifield. …

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