Backscattering strength and the range dependence of sound scattered from the ocean surface

The wind-driven ocean surface has been modeled as a conjoint assemblage of finite wedges such that the ocean statistics are correctly represented as a function of wind speed alone. The impulse response due to wedge diffractions and facet reflections from this surface has been calculated by the Biot–Tolstoy theory [J. Acoust. Soc. Am. 29, 381–391 (1957)]. After transformation to frequency space, the range dependence of the scattered intensity is found to vary from R−2 to R−4 depending on range, percentage of reflecting facets, and ratio of surface height correlation length to sound wavelength. It is proposed that the concept of backscattering strength be redefined as BSS=10 log10(IBS/I0)[(RN+2)/RN0A], where I0 is source intensity at R0=1 m; A, scattering area; R, range in meters; and IBS, backscattered intensity. The exponent 0?N?2 may be determined experimentally, at sea, or as shown in these calculations.