Table 7.

Ridge regression results on NA.

K = 0.185	Nonnormalized coefficient		Normalized coefficient	t	P	R2	Adjusted R2	F
	B	Standard error	Beta
Constant	1.055	2.788	–	0.379	0.707	0.965	0.961	251.753(0.000***)
Hydroacoustics	0.16	0.025	0.168	6.295	0.000***
Windy sound	0.09	0.033	0.065	2.718	0.009***
Birdsong	0.275	0.022	0.296	12.765	0.000***
Insect chirping	0.086	0.027	0.087	3.126	0.003***
Combined sound	0.345	0.019	0.394	18.507	0.000***

1. Dependent variable: NA 2. ***, ** and * represent significance levels of 1%, 5% and 10% respectively.