Statistical Analysis
Continuous variables were examined using the Shapiro–Wilk test for normality. For continuous variables of normal distribution, the data were presented as means ± standard deviation (SD). For the non-normal distribution, the data were presented as medians (ranges). Spearman’s rank correlation was used to investigate the relationship between the percentage of noise duration and the actual monitoring time. The p-values are two-sided. A p-value of < 0.05 was considered to indicate statistical significance. All statistics were calculated using R statistical software (version 2.13.0, R Foundation for Statistical Computing, Vienna, Austria).