Cardiac responses caused by shots of tanks during sleep

Abstract Heart rate responses evoked by military noise were registered in 17 subjects. The subjects slept in the laboratory during 13 consecutive nights each. Prerecorded shots of tanks with peak levels from 78 to 82 dB(A) were played back every three nights, either during the first three hours after lights off or during the last three hours before awakening. The shots provoked a brief acceleration of the heart rate. The extent of the response was larger during sleep than when awake, and larger in women than in men; it was larger in the early morning than in the first hours after sleep onset. Within one night no adaptation took place; a limited habituation, however, was observed during the test series.