Acoustic and perceptual indicators of emotional stress

Tape recordings of telephone conversations of Consolidated Edison's system operator (SO) and his immediate superior (CSO), beginning an hour before the 1977 New York blackout, were analyzed for indications of psychological stress. (SO was responsible for monitoring and switching power loads within the Con Ed network.) Utterances from the two individuals were analyzed to yield several pitch and amplitude statistics. To assess the perceptual correlates of stress, four groups of listeners used a seven-point scale to rate the stress of SO and CSO from either randomized vocal utterances or transcripts of the randomized utterances. Results indicated that whereas CSO's vocal pitch increased significantly with increased situational stress, SO's pitch decreased. Listener ratings of stress from the voice were positively related to average pitch. It appears that listener's stereotype of psychological stress includes elevated pitch and amplitude levels, as well as their increased variability.