Mid-frequency acoustic localization of breaking waves

During an experiment in deep water off the coast of Southern California, winds between 20 and 25 knots resulted in large breaking waves. A mid-frequency planar hydrophone array recorded underwater ambient noise while an airplane equipped with a high-resolution video camera recorded images of the sea surface above the array. Beams of ambient noise between 5 and 6kHz were projected onto the sea surface and aligned in space and time with the aerial images. The array’s resolution of the surface is coarse (20 by 50 m) due to its modest 1 meter horizontal aperture and relatively deep 130meter deployment depth. Nonetheless, concentrated regions of high intensity in the acoustic surface projection match visible breaking events in the aerial images. [Work supported by the Office of Naval Research.]