Figure 4: In this 1-hour period, eight aircraft noise events with maximum sound pressure levels of 65 dB(A) were played back in the laboratory with seven or eight minute intervals between playbacks. The heart rate trace is shown in the upper part of the figure, the hypnogram in the lower part. Rechtschaffen et al. sleep stages are given on the right side of the figure (W=wake, REM=rapid eye movement sleep, S1/S2/S3=sleep stages 1/2/3). Times of aircraft noise event playbacks (Noise) are given below the hypnogram as black diamonds. Times of automatic ECG activation recognition by the ECG algorithm (ECG-Act) are given above the hypnogram also as black diamonds. Adopted from Basner et al.