Acoustic propagation in the ocean with a porous bottom

Abstract

Biot's theory was directly incorporated with the normal mode analysis of acoustic propagation in the ocean with a porous elastic bottom. The complex dispersion relations was obtained in a closed form for the case of a homogeneous ocean with a poro-elastic half-space. The attenuation data from the shallow water experiments in the Mediterranean Sea were compared with the theoretical calculations. The 100-m water/sandy bottom data showed an optional transmission frequency of about 250 Hz. The theoretical analysis using the sediment data revealed that the attenuation of the high-frequency components are mainly due to the seepage of pore water through the sand (the slow compressional wave effect) and the attenuation of the low-frequency components are owing to the energy dissipation of the shear waves by the Coulomb friction in the consolidated sand. As a result, the intermediate frequency components have minimum overall attenuations and result into the optimal transmission frequencies. The agreements between the theory and the experiments are good. [Work supported by NSF.]