Acoustic Propagation in Gassy Sediments
Abstract
Gas bubbles are ubiquitous in organic-rich, muddy sediments of coastal waters and shallow adjacent seas (Judd and Hovland, 1992; Richardson and Davis, 1998). Depths and horizontal distributions of these gas-charged sediments are usually determined from seismic profiling. The presence of gas bubbles often impedes acoustic characterization of sediments below the gas horizon and terms such as acoustic masking or blanking, acoustic turbidity, bright spots, wipeouts, and pulldowns are used to characterize these gas- charged sediments. Acoustic turbidity also produces anomalously high acoustic backscattering from the seafloor (Lyons et al., 1996; Tang, 1996) degrading the effectiveness of high-frequency sonar. Models of acoustic- bubble interactions in fine-grained sediments developed by Anderson and Hampton (1980) have been corroborated by laboratory (Gardner, 2000) and field (Wilkens and Richardson, 1998; Lyons et al., 1996; Tang, 1996, Anderson et al., 1998) experiments. In this paper, we model the effects of bubble volume, bubble size and bubble distribution on sound speed and attenuation in the well-characterized sediments of Eckernforde Bay, Baltic Sea and from experiments recently conducted in Cape Lookout Bight, North Carolina. These two areas constitute the best known and most studied area of gassy sediment in the world (Richardson and Davis, 1998; Martens et al., 1998) thus providing the ideal settings for such comparisons.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 23, 2000
- Accession Number
- ADA393660
Entities
People
- Mike Richardson
- Warren T. Wood
Organizations
- United States Naval Research Laboratory