Acoustic propagation and ambient noise in the Philippine Sea: The 2009 and 2010-2011 Philippine Sea experiments.

The 2010–2011 North Pacific Acoustic Laboratory Philippine Sea experiment (PhilSea10) combines measurements of acoustic propagation and ambient noise with the use of acoustic remote sensing to characterize the oceanographically complex Philippine Sea. The goals are to (i) understand the impacts of fronts, eddies, and internal tides on acoustic propagation; (ii) determine whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions and for understanding the local ocean dynamics; (iii) improve our understanding of the physics of scattering by small-scale oceanographic variability; and (iv) characterize the depth dependence and temporal variability of the ambient noise field. The PhilSea10 experiment was preceded by a pilot study/engineering test in April–May 2009 (PhilSea09) to obtain an initial look at propagation and ambient noise in the Philippine Sea, study short-term variability using long-duration transmissions, and test equipment to be used in 2010–2011. In both experiments, a combination of moored and ship-suspended low-frequency acoustic sources transmit to a newly developed distributed vertical line array receiver capable of spanning the water column in deep water. In 2009, the towed five octave research array also recorded the transmissions. [Work supported by ONR.]