Table 9. Summary of heart rate variability according to noise level and as stratified by NS (low NS).

Characteristics	Low NS (road traffic) (n = 63)		F	P value	Low NS (aircraft) (n = 22)		F	P value
	Low noise (n = 43)	High noise (n = 20)			Low noise (n = 11)	High noise (n = 11)
HR	74.85 ± 6.69	75.53 ± 7.92	0.164	0.687	75.98 ± 4.56	75.91 ± 7.26	0.020	0.890
RMSSD	64.54 ± 34.97	53.52 ± 30.79	1.618	0.208	65.56 ± 25.57	52.60 ± 24.05	1.215	0.284
SDSD	0.06 ± 0.04	0.05 ± 0.03	1.363	0.248	0.07 ± 0.03	0.05 ± 0.02	1.306	0.267
NN50	112.94 ± 57.88	99.77 ± 69.93	0.599	0.442	125.42 ± 50.38	100.23 ± 58.40	0.892	0.357
pNN50	33.53 ± 19.26	28.96 ± 21.93	0.689	0.410	36.66 ± 18.07	29.09 ± 18.05	0.749	0.398
LF	1,892.44 ± 1,532.79	1,313.60 ± 1,234.91	2.042	0.158	1,884.62 ± 574.59	1,320.73 ± 1,072.49	2.003	0.173
HF	1,993.64 ± 2,393.43	1,371.98 ± 1,578.48	1.327	0.254	1,899.00 ± 1,385.32	1,194.37 ± 910.29	1.770	0.199
TP	9,587.86 ± 7,971.52	6,260.15 ± 4,784.89	3.075	0.850	8,758.93 ± 2,828.35	7,647.88 ± 6,495.13	0.361	0.555
RATIO	1.35 ± 0.59	1.62 ± 1.22	1.028	0.315	1.43 ± 0.77	1.21 ± 0.44	0.467	0.503
nLF	51.75 ± 11.68	51.59 ± 17.82	0.010	0.920	52.52 ± 13.87	49.80 ± 9.20	0.195	0.664
nHF	48.25 ± 11.68	48.41 ± 17.82	0.010	0.920	47.48 ± 13.87	50.20 ± 9.20	0.195	0.664

Data are shown as mean ± standard deviation.

NS = noise sensitivity, HR = heart rate, RMSSD = root mean square of successive difference of successive normal-to-normal, SDSD = standard deviation of successive differences, NN50 = difference between adjacent normal-to-normal intervals of 50 ms or more, pNN50 = NN50/total number of all normal-to-normal, LF = power in low-frequency range, HF = power in high-frequency range, TP = total power, RATIO = LF/HF ratio, nLF = low-frequency power in normalized units, nHF = high-frequency power in normalized units.