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. 2014 May 16;13:37. doi: 10.1186/1476-069X-13-37

Table 2.

Spearman correlations between frequency components of road noise levels and traffic flow rates

Vehicle type Traffic flow number Median (Q1-Q3) (vehicle/hr) Correlation coefficients
Low frequency
 Medium frequency
 High frequency
31.5 Hz 63 Hz 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz 8000 Hz
MC
 42
 494 (280–704)
 0.505a
 0.594a
 0.574a
 0.488b
 0.351c
 0.279
 0.312c
 0.493a
 0.395a
LDGV
 42
 600 (360–1032)
 0.630a
 0.592a
 0.515a
 0.356c
 0.276
 0.248
 0.204
 0.301
 0.218
LDDT
 42
 138 (80–228)
 0.398b
 0.371c
 0.491b
 0.313c
 0.110
 0.162
 0.147
 0.132
 0.093
HDDT
 42
 42 (24–80)
 0.482b
 0.539a
 0.456b
 0.350c
 0.301
 0.252
 0.233
 0.271
 0.213
Total 42 1552 (764–2132) 0.601a 0.643a 0.586a 0.457b 0.331c 0.272 0.274 0.393c 0.340c

HDDT = heavy-duty diesel trucks; LDDT = light-duty diesel trucks; LDGV = light-duty gasoline vehicles; MC = motorcycles; Q1 = first quartile; Q3 = third quartile. aP < 0.001. bP < 0.010. cP < 0.050.