Low-frequency sound generation from breaking surf

Abstract

An existing collective oscillation model for low-frequency sound generation from an open-ocean wave is extended to the surf zone. The hemispherical geometry of the open-ocean breaking wave entrained bubble cloud is replaced by a prolate hemispheroidal cloud. A Green’s function is obtained for a point source within this cloud. The far-field acoustic intensity is then computed for a distribution of point sources within a cloud. It is hypothesized that cloud resonances, assuming a “long” orientation is applicable, are determined by the minor-axis length for cloud sizes observed in the surf zone at frequencies of interest here.