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The effect of wind-generated bubbles on sea-surface backscattering at 940 Hz
Robbert van Vossen1, Michael A Ainslie
1TNO, Oude Waalsdorperweg 63, P.O. Box 96864, 2509 JG The Hague, The Netherlands. robbert.vanvossen@tno.nl
The Journal of the Acoustical Society of America
|November 18, 2011
Summary
Predictions of sea-surface backscattering strength are challenging at low frequencies. This study shows that scattering from individual resonant bubbles, not just bubble clouds, can explain sonar performance data.
Area of Science:
- Ocean acoustics
- Acoustic scattering
- Sonar performance modeling
Background:
- Sea-surface backscattering strength predictions are crucial for sonar performance.
- Measurements at small grazing angles relevant to low-frequency active sonar (1-3 kHz) are scarce.
- Understanding scattering mechanisms is key for accurate theoretical predictions.
Purpose of the Study:
- To investigate individual resonant bubbles as a sea-surface backscattering mechanism.
- To develop a scattering model incorporating resonant bubbles and rough surface scattering.
- To validate the model against Critical Sea Test (CST) measurements.
Main Methods:
- Derived a theoretical scattering model including individual resonant bubbles.
- Incorporated rough surface scattering into the model.
- Fitted model results to CST measurements at 940 Hz, parameterizing large bubble concentration.
Main Results:
- The model successfully explains CST data.
- A small number of large resonant bubbles can account for the observed scattering.
- This indicates resonant bubbles are a significant alternative to bubble clouds.
Conclusions:
- Individual resonant bubbles represent a viable mechanism for sea-surface backscattering at low frequencies.
- The developed model provides a new tool for sonar performance prediction.
- Further research should explore the prevalence and impact of resonant bubbles in various sea states.
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