High-Frequency Volume Scattering from Gassy Sediments
Conference proceedings 10-13 Jul 2000
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS MARINE GEOSCIENCES DIV
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Measurements of values of sediment physical properties, bubble volume, and bubble size distribution are used to predict frequency-dependent sound speed and attenuation in the fine-grained gassy sediments of Eckernforde Bay, Baltic Sea. Acoustic models 1-3 predict, at acoustic frequencies well-above resonance, that sound speed is unaffected by bubbles and scattering from bubbles dominates attenuation. At frequencies well below resonance, sound speed is much lower than bubble-free sediments and attenuation is dominated by scattering from impedance contrasts. Near-resonance sound speed varies greatly with frequency and attenuation is very high. Given the highly variable spatial and temporal distribution of bubble volume, bubble size, and bubble size distribution in Eckernfdrde Bay, the agreement between theoretical predictions and acoustic measurements is remarkably good.