Distribution of sleep stages in baseline and noise nights and their differences. Comparisons are based on the shorter sleep period time (SPT). Mean values were calculated for each of the n = 48 subjects in order to account for non-independent data. 395 noise and their corresponding baseline nights were analyzed in total. As the assumption of normally distributed data was denied by the Shapiro-Wilk-Test for the differences in Wake and REM non-parametric p-values derived by the Wilcoxon matched pairs signed rank sum test are also given for these categories.