Seabed reflection measurement results shed light on theories of acoustic propagation in marine sediments

Abstract

Marine sediments are inherently a complex assemblage of solid particles (of size ranging over five orders of magnitude) with fluid-filled interstices sometimes containing gas. The mechanisms that govern the dispersive wave speeds and concomitant attenuation are still hotly debated. In order to shed light on the mechanisms and current theoretical approaches to approximating them, measurements of in-situ sediments are desirable since they provide the natural complexity desirable for testing theories against realistic sediment structures. On the other hand, in-situmeasurements present significant challenges since seabed effects must be separated from other ocean processes, e.g., water column variability, biologics and sea surface roughness, and bubbles. Seabed reflection measurements offer one way to mitigate unwanted ocean processes. Reflection-derived observations are presented that shed light on current sediment acoustic models. In addition, experiments are proposed which will further test and help guide sediment acoustics theoretical developments. [Work supported by the ONR Ocean Acoustics Program.]Marine sediments are inherently a complex assemblage of solid particles (of size ranging over five orders of magnitude) with fluid-filled interstices sometimes containing gas. The mechanisms that govern the dispersive wave speeds and concomitant attenuation are still hotly debated. In order to shed light on the mechanisms and current theoretical approaches to approximating them, measurements of in-situ sediments are desirable since they provide the natural complexity desirable for testing theories against realistic sediment structures. On the other hand, in-situmeasurements present significant challenges since seabed effects must be separated from other ocean processes, e.g., water column variability, biologics and sea surface roughness, and bubbles. Seabed reflection measurements offer one way to mitigate unwanted ocean processes. Reflection-derived observations are presented that shed light on current sediment acoustic models. In addition, experiments are proposed which will further test and help guide ...