Measurements and modeling of sound propagating into unconsolidated water-saturated porous media in a laboratory environment

Abstract

Three models of sound propagating into and within a water-saturated sandy bottom are compared to measurements made in the NRL shallow water laboratories. An initial set of measurements was made in a manufactured 212-μm mean diameter sand, which was washed and filtered, to quantify sound penetration as a function of incident angle and interface roughness, as well as to identify the wave types generated within a water-saturated sandy bottom. Measurements have also been made of sound propagation within a water-saturated sandy bottom, which employed a specialized set of transducers to generate and measure compressional waves and a second set of transducers to generate and measure shear waves. Measurements have also been made in a 525-μm mean diameter water-saturated sand. All of the above measurements are compared to a fluid bottom model and a Biot media model, both of which characterize the sound propagating within a water-saturated sandy bottom. In addition, the measurements of sound penetration into the standy bottom are compared to roughened interface scattering models. [Work supported by NRL and ONR.]