High-frequency acoustic penetration of ocean sediments

Abstract

Two experiments were conducted to investigate acoustic penetration of ocean sediments: one in a muddy site in the Baltic Sea and the other in a sandy site in the Gulf of Mexico. In both experiments, acoustic sensors were placed in the sediment to measure the acoustic signals. The signals are processed coherently to give direction and speed of the acoustic waves. The data from the two sites give very different results. In the muddy site, the sediment sound speed is very close to that of the water, the situation in the sandy site is more complicated. The medium is treated as a poro-elastic solid governed by Biot’s theory of acoustic propagation. For the sandy site, the theory predicts two acoustic waves, one faster than the sound speed in water, and the other slower. Comparisons are made between theory and experiment. [Work supported by Office of Naval Research, under the Coastal Benthic Boundary Layer (CBBL) Special Research Program.]