On sound scattering and attenuation in suspensions, with marine applications

Abstract

The theory of sound scattering and attenuation by a mobile, elastic sphere in a viscous, heat-conducting fluid is formulated in terms of phase angles for the partial scattered waves. The solution reduces in the appropriate limit to that for the inviscid, nonconducting case. Specializing to the long-wavelength limit, an important case in marine acoustic remote sensing applications, expressions are obtained for the sound pressure amplitude of the scattered wave including the effects of viscous and thermal absorption at the fluid–particle interface. Furthermore, an expression is obtained for the ratio of thermal to viscous absorption and it is shown that this ratio is small for particles with bulk densities greater than 1.3–1.7 g cm−3 suspended in water, depending upon the thermal and elastic properties of the solid, and provided the acoustic frequency is such that the skin depths of the thermal and viscous waves are less than the particle radius.