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| 3-D Audio Traffic Alert and Collision Avoidance System |
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Principal Investigators
Durand R. Begault SJSUF: 415-604-3920 Elizabeth M. Wenzel ARC:
Problem
The current implementation of the Traffic Alert-Collision Avoidance System (TCAS II) uses both auditory and visual information to supply flight crews with real-time data and instructions about proximate aircraft. Spatial information is currently derived from a "head- down" map display in the instrument panel; the auditory warning conveys no spatial information and is used only as an alert. Visual gaze must first be directed down towards the map display, and then upwards for search of the traffic "target," which is inefficient compared to target acquisition by immediately directing the gaze to the correct direction out the window.
Approach and Objectives
We have used virtual acoustic (3-D audio) techniques to form a head-up auditory display (Figure 1.2) for TCAS traffic advisories by processing the aural alert so that its perceived direction comes from the relative direction of intruding traffic. Immediate spatial situational awareness is conveyed, allowing faster acquisition of traffic "targets" while keeping the crew member's gaze out-the-window. Also, by accessing an alternative perceptual modality-sound-the visual perceptual modality is freed to concentrate on other head-down tasks when necessary.
Accomplishments
A prototype hardware setup has been designed and installed within a generic "glass cockpit" flight simulator. With this system, the out-the-window position of the traffic can be linked to the virtual auditory position of the word "traffic" heard through headphones. Two full-mission simulation studies compared target acquisition time and the number of targets acquired between control and experimental conditions (with and without 3-D audio). An initial experiment, designed to contrast performance using a spatial versus a non-spatial auditory TCAS advisory, showed that the time interval for traffic acquisition was reduced by about 2.2 seconds when 3-D sound cues were used. In a second experiment, two conditions were compared for target acquisition time: a standard head-down TCAS display versus a 3-D audio TCAS display. Results showed a significant difference in target acquisition time between the two conditions, favoring the 3-D audio TCAS condition by 500 ms.
Future plans
An aural 3-D TCAS display may be desirable in addition to a standard TCAS display in an operational setting. This is because pilots can keep their head "out the window" looking for traffic without needing to move the head downwards to the planform map display and then back up. In an actual cockpit with 3-D sound added to the current TCAS system, the pilot flying could use the auditory information for immediate head up search while the pilot not flying could gain numerical altitude information and verify the direction for the other pilot. An experiment scheduled for April 1996 will focus on evaluating the combination of the two systems.
Key references
Begault, D. R. (1993): Head-up Auditory Displays for Traffic Collision Avoidance System Advisories: A Preliminary Investigation. Human Factors 35, 707-717.
Begault, D. R. (1995): Head-up auditory display research at NASA Ames Research Center. Proceedings of the 39th Annual Human Factors and Ergonomics Society Meeting pp. 114-118. Santa Monica, CA: Human Factors Society.
Begault, D. R., and Pittman, M. T. (In Press (February 1996)): Three- Dimensional Audio Versus Head-Down Traffic Alert and Collision Avoidance System Displays. International Journal of Aviation Psychology 6, 79-93.
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