Low-frequency sound generation by an individual open-ocean breaking wave

Bubble cloud resonances have been proposed as an explanation of the low-frequency acoustic radiation produced by breaking waves. A previous model [H. N. Oguz, J. Acoust. Soc. Am. 95, 1895-1912 (1994)] considered excitation of the bubble cloud by a rigid piston at the base of a hemispherical bubble cloud. The present model considers excitation of the cloud by individual point sources within the cloud. A Green's function is obtained for a point source displaced from the origin of a hemispherical bubble cloud beneath a pressure release surface. The method of images and superposition allow one to obtain the field generated by a distribution of point sources within the bubble cloud. The frequency-dependent radiation pattern for two distributions of point sources within the cloud is obtained. Distributing the point sources within the forward sector of the bubble cloud generates spectral characteristics consistent with measured open-ocean breaking wave spectra.