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Low frequency sound scattering from spherical assemblages of bubbles using effective medium theory
1University of Miami, RSMAS, AMP, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA.
The Journal of the Acoustical Society of America
|February 6, 2008
Summary
This study models acoustic scattering from underwater bubble or fish schools using effective medium theory. The findings enable simultaneous determination of school size and density from acoustic data.
Area of Science:
- Acoustics
- Fluid Dynamics
- Biophysics
Background:
- Underwater acoustic scattering from bubble or fish schools is complex.
- Effective medium theory (EMT) offers a framework for understanding collective scattering phenomena.
Purpose of the Study:
- To theoretically determine the acoustic field scattered by underwater assemblages of resonant scatterers.
- To develop a method for simultaneous inversion of assembly radius and void fraction.
Main Methods:
- Application of effective medium theory to spherically shaped assemblages.
- Derivation of scattering amplitude and cross-section expressions using S-matrix methods.
- Analysis of low-frequency collective resonances and breathing modes.
Main Results:
- Explicit expressions for scattering amplitude, cross sections, resonance frequency, and spectral shape.
- Demonstrated validity through application to fish schools with swim bladders.
- Excellent agreement between analytical results and numerical benchmark computations.
Conclusions:
- The developed effective medium theory accurately predicts acoustic scattering from dense bubble and fish schools.
- The approach allows for direct inversion of physical parameters from scattering cross sections.
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