Academic journal article Human Factors

Auditory Spatial Facilitation of Visual Search Performance: Effect of Cue Precision and Distractor Density

Academic journal article Human Factors

Auditory Spatial Facilitation of Visual Search Performance: Effect of Cue Precision and Distractor Density

Article excerpt

INTRODUCTION

Virtual environments often contain simulations of auditory reality in addition to visual reality. Auditory virtual environments are produced by replicating two cues known to be important for sound-source localization: inter-aural difference cues and cues related to the action of the pinna on incoming sources (e.g. Wenzel, Wightman, & Foster, 1988; Wightman & Kistler, 1989). The pinna cues are replications of the magnitude and phase characteristics of the head-related transfer function (HRTF) and produce the perception of externalized sound images at a particular elevation and azimuth when presented via earphones. These three-dimensional (3D) audio cues have been credited with performance improvements in many settings for both auditory and visual tasks in real- and virtual-displays. Benefits to auditory tasks include improved speech intelligibility, audio feedback and alerts in the cockpit, and improved acoustic-signal recognition in sonar systems (Begault, 1995; Doll & Hanna, 1997; McKinley & Ericson, 1997). In visual tasks, auditory 3D cues can improve traffic detection and avoidance, target acquisition, and visual workload in the cockpit (Begault, 1993; McKinley et al., 1995; McKinley & Ericson, 1997).

Auditory 3D cuing benefits visual search performance because auditory 3D displays take advantage of the strengths of the auditory system relative to vision. Although the visual system is vastly superior to the auditory system on spatial acuity tasks, the human auditory system can detect and localize sounds from any direction around the listener without any movement of the sensory apparatus (e.g., Middlebrooks & Green, 1991). Furthermore, auditory events are localized in reference to the position of the listener (e.g., Fisher & Freedman, 1968; Perrott, Saberi, Brown, & Strybel, 1990). Using auditory spatial cues to indicate the location of a visual target exploits the omnidirectional attribute of the human auditory system and provides a natural means of cuing an observer, such as a pilot, as to visual events in the environment.

In the laboratory, auditory spatial cues significantly reduce the time to find visual targets. Perrott et al. (1990) demonstrated that the time to locate and identify a single visual target in a 260 [degrees] horizontal search field was reduced by 150 to 800 ms when an auditory stimulus, located at the target, was presented simultaneously with the target. When vertical uncertainty was added to the task, the facilitation increased to approximately 1000 ms. Perrott, Cisneros, McKinley, and D'Angelo (1995, 1996) measured the effect of auditory spatial cues in a visual search task with a 360 [degrees] horizontal by 160 [degrees] vertical search field. In the absence of auditory spatial information, search times were lowest ([less than] 1250 ms) for targets within 50 [degrees] horizontally and 40 [degrees] vertically. When auditory cues were spatially coincident with the visual target, search times were less than 1250 ms for nearly the entire search field.

Although the greatest benefits of auditory spatial cuing are accrued for peripheral targets, search performance also improves when the targets are located in the central visual field. Perrott et al. (1990) obtained reductions of 150 to 200 ms for visual targets within 10 [degrees] of fixation. Perrott, Sadralodabai, Saberi, and Strybel (1991) found the benefits of auditory spatial cues in the central visual field to depend on target distance and the number of visual distractors present. For targets located within 2.4 [degrees] of fixation, search times fell by 30 ms when auditory spatial cues were present. When the targets were located 15 [degrees] from fixation, the auditory spatial cue lowered search times by 100 ms and minimized the effects of number of distractors. The slope of search time as a function of number of distractors in the auditory spatial cue condition was nearly half that of the no-cue condition (4. …

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