HR: 0800h
AN: NS31B-0394    [Abstracts]
TI: Investigating the acoustic properties of gassy marine sediments: Results of Laboratory experiments
AU: * Robb, G B
EM: gbor199@noc.soton.ac.uk
AF: National Oceanography Centre (Southampton), Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Leighton, T G
EM: T.G.Leighton@soton.ac.uk
AF: Institute of Sound and Vibration Research, University of Southampton, Southampton, SO17 1BJ, United Kingdom
AU: Dix, J K
EM: jkd@noc.soton.ac.uk
AF: National Oceanography Centre (Southampton), Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Best, A I
EM: aib@noc.soton.ac.uk
AF: National Oceanography Centre (Southampton), Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Humphrey, V F
EM: vh@isvr.soton.ac.uk
AF: Institute of Sound and Vibration Research, University of Southampton, Southampton, SO17 1BJ, United Kingdom
AU: Klusek, Z
EM: Klusek@iopan.gda.pl
AF: Institute of Oceanography, Polish Academy of Sciences, Sopot, PO Box 148, Poland
AB: The acoustic properties of marine sediment containing free gas bubbles are considerably more complex, and therefore more poorly understood, than the acoustic properties of saturated sediment. A more detailed understanding of gassy sediments would therefore be advantageous to a wide range of marine users, ranging from marine surveyors to those responsible for homelands defence. To provide a simplified system through which the acoustic properties of gassy sediments can be investigated, laboratory experiments have been performed. Samples of both gassy mud and a synthetic bubbly gel mimic were examined. Results for the compressional wave velocity and attenuation coefficient are presented from 30 to 110 kHz. These are compared to the predictions of linear theoretical models for both sediment and water based bubble distributions. In addition, the results of combination frequency techniques are presented. These exploit the non linear interaction between the acoustic field the bubbles, therefore allowing bubble size distributions to be inferred though the analysis of the sum and difference frequency scattered fields. All of the results are compared to bubble size distributions measured independently using a X-Ray CT scanner, which is able to resolve bubbles with radii greater than 20 micrometers.
DE: 3004 Gas and hydrate systems
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
DE: 4455 Nonlinear waves, shock waves, solitons (0689, 2487, 3280, 3285, 4275, 6934, 7851, 7852)
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting