SOUND-SCATTERING BY RANDOM VOLUME INHOMOGENEITIES WITH A FRACTAL SPECTRUM

Sound scattering by random volume inhomogeneities (refractive index fl uctuations) in the ocean is considered in the approximation of the sma ll perturbation method. The inhomogeneities ale assumed to be highly a nisotropic, namely, small-scale in depth and large-scale in the horizo ntal plane, which is specific to an oceanic medium. The large-scale in homogeneities are fractals with the dimension D = 1.5. The scattering of sound by fractals results in attenuation described by the frequency dependence beta similar to f(3/2). It was found that the fractal dime nsion of the inhomogeneities coincides with the exponent in the freque ncy dependence of the attenuation coefficient, which is specific to un ordered fractal media; the fractal dimension of fractal inhomogeneitie s in the ocean is close to that of clouds in the atmosphere (1.35 < D < 1.41). Thus, it is concluded that, in the first approximation, the l arge-scale inhomogeneities in the ocean are fractals. However, after a more detailed consideration, oceanic inhomogeneities, as well as clou ds in the atmosphere, may prove to be multifractals with an inherent s pectrum of fractal dimensions close to D = 1.5. The fractal origin of low-frequency sound attenuation in an oceanic underwater channel can b e regarded as an established fact.