Instantaneous change in transient shift of sleep stage in response to passing truck noise.

The transient effects of passing truck noise on sleep stage shift were examined in fifteen male students aged 19-21 years old for 7 to 11 non-consecutive nights. Shift percentage for proceeding from Stage 2 to shallower stages (Stage 1, waking or movement time) as well as that from Stages 3 to 2, Stage 1, waking or movement time were determined. Change in Stage REM by noise was examined for shift to other stages. The percentage for shallower stages from Stage 2 significantly increased by exposure to 45, 50, 55 and 60 dBA noise compared to the non-exposed control, though this was not observed in Stage REM. The percentage of shift to shallower stages from Stage 3 significantly increased at 50, 55 and 60 dBA noise compared to the control. The minimum effective sound level for the percentage of shift to shallower stages from Stage 2 by the passing truck noise was less than 45 dBA, while that for the percentage of change in Stage REM was greater than 60 dBA and that for the percentage of shift to shallower stages from Stage 3 by the noise was between 45 and 50 dBA. Responses to noise exposure in Stage REM was less sensitive than in Stage 3.