Acoustic Reverberation from Bubble Plumes in the Ocean: Do Multiple Scattering Processes Play a Significant Role?
1997
Feuillade, Christopher
Acoustic scattering from ocean bubble plumes has recently increased in importance as a cause of sea surface reverberation. With the development and application of high frequency SONAR equipment, the question has arisen as to whether multiple scattering processes between strongly resonating bubbles significantly affects reverberation levels. This report describes a comparison of two sets of experimental data with both the classic theory of linear acoustic propagation in bubbly water, and a recently published new theory which includes multiple scattering effects. The results of the analysis indicate that, for water containing bubbles of uniform size with volume fractions beta > or = 0.22%, multiple scattering effects strongly influence acoustic behavior. However, when beta < 0.22%, the effects of multiple scattering appear to diminish quite sharply. Also, for nonuniform bubbles and beta approx. equal 0.02%, the analysis shows that multiple scattering effects have no observable effect. The overall implication of these results is that, for realistic compositions of bubbly water found in the ocean, multiple scattering effects do not affect the attenuation and dispersion of sound, and may be neglected. Consequently, the classic theory should be completely adequate to describe acoustic scattering and reverberation levels from ocean bubble plumes.
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