Statistical analysis of northern Philippine Sea underwater sounds

The deep ocean experiment, PhilSea09, was conducted April–May, 2009, in the central part of the northern Philippine Sea. The deep 1000-m section of the distributed vertical line array (DVLA), which was composed of 30 elements (upper 10 at 90 m spacing starting at 4285 m depth, and 5 m spacing for the deepest 20 elements over the depths 5185–5280 m), recorded primarily four types of sounds not created as part of the experiment: wind noise, ship noise, airgun signals, and earthquake T-phases. The statistical properties of these sounds are examined quantitatively using non parametric statistical tests operating on the single element and beam level narrowband envelope time series. These statistical tests include the Wald-Wolfowitz runs test for mutual independence of the data samples, the Kolmogorov-Smirnov two-sample test for stationarity, and the Lillifors test for Gaussianity. One result is that these sounds, except for wind-dominated noise, fail the test for Gaussianity. Higher-order spectral analysis is ...