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Voice Stress Analysis as a Measure of Operator Workload

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Technical memo. Feb 1978-Dec 1979

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This study attempted to determine if the Psychological Stress Evaluator PSE could be used to detect the amount of situational stress in the voice while subjects performed a four-choice information processing task at different presentation rates. The 42 subjects were divided into group I - Jet, group II - Prop, and group III - Staff. A Response Analysis Tester RATER presented a four-choice discrimination task in which the subjects were required to match a response key to each of four stimuli appearing in a display window. The sequence of stimuli was randomly presented in an automatic-paced mode for nine 1-min tests. The stimuli presentation rates were set at one symbol per 1.5 sec, .75 sec, and .50 sec. At the end of each block of three tests, the subjects estimated self-performance as percent correct and rated stress on a scale of one no stress to seven high stress. Voice signals were initially recorded on magnetic tape, then processed through filtering circuits and displayed on a strip chart for subsequent visual analysis and interpretation. A subjective scoring criterion was established and then translated into electronic equivalents and automated on a Varian 73 computer for voice pattern recognition analysis. Significant main effects for percent-correct responses were obtained for groups, presentation rate, and groups X presentation rate interaction. No significant differences were found in the correct responses of the subjects when the number was verbalized or not verbalized. The Staff group produced significantly fewer correct responses than either the Jet or Prop groups at the .75 sec rate. Voice stress analysis showed significant correlations with performance scores and stress ratings of a selected pool of subjects. Discussion includes the potential application of an objective, reliable, sensitive, and nonobtrusive measure of stress in vocal communication systems that require operator workload assessments.

Subject Categories:

  • Military Aircraft Operations
  • Psychology
  • Personnel Management and Labor Relations

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