Subjects were exposed to four simulated 'indoor' sonic booms over an approximate thirty-minute period. The overpressure levels were 1.0, 2.0 and 4.0 psf (as measured 'outdoors') with durations of 295 milliseconds. Subjects performed a two-dimensional compensatory tracking task during the exposure period and continuous recordings were obtained of heart rate and skin conductance. No evidence of performance impairment was found for any of the overpressure levels. Rather, performance improved significantly following boom stimulation along with heart-rate deceleration and skin conductance increase. The obtained pattern suggests that the simulated booms may have elicited more of an orienting or alerting response than a startle reflex. The results are discussed in terms of the possible importance of rise time as a determinant of the physiological and performance effects which may be produced by sonic booms. Since faster rise times of the simulated booms might have increased loudness sufficiently to change these results considerably, care should be taken to avoid drawing unwarranted conclusions, relative to general sonic boom effects, on the basis of these findings alone. (Author).