How does the integration of speech recognition controls and spatialized auditory displays affect user workload?

The purpose of this study was to determine the effects of the integration of automatic speech recognition (ASR) controls and spatial audio displays on soldier workload in noisy, cognitively demanding environments such as armored vehicles. To achieve this end, measures of mental workload were obtained in tasks in which subjects were instructed to give ASR voice commands in response to simulated radio messages, while simultaneously performing a tank-driving task in the presence of different levels of ambient tank noise. Independent variables were type of auditory display, number of talkers giving simultaneous radio output to the listener, and background noise level. The dependent variable was overall subject workload ratings as measured by the National Aeronautics and Space Administration Task Load Index (NASA TLX). The workload data indicated that spatialized audio radio communications, used with and without head trackers, significantly decreased overall workload in the radio communication task. There were no other significant effects. These data support the human performance data described in Haas [1], which is the same study in which the workload data was obtained. The need for workload measures that examine multiple interfaces is discussed, and a human performance and workload modeling tool is recommended.