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Robust time reversal focusing in the ocean
Seongil Kim1, W A Kuperman, W S Hodgkiss
1Marine Physical Laboratory, Scripps Institution of Oceanography, La Jolla, California 92093-0238, USA. sikim@add.re.kr
The Journal of the Acoustical Society of America
|July 26, 2003
Summary
Time-reversal focusing in dynamic ocean environments is limited by sound speed fluctuations. New methods improve stable focusing duration by analyzing experimental and simulation data.
Area of Science:
- Underwater acoustics
- Ocean acoustics
- Wave propagation
Background:
- High-frequency acoustic transmissions (3.5 kHz) in dynamic ocean environments face limitations in stable time-reversal focusing.
- Time-dependent ocean conditions cause dynamic variations in vertical focal structure, including splitting and remerging, leading to significant focal intensity changes.
Purpose of the Study:
- To investigate the causes of limited stable focusing in time-reversal experiments.
- To develop methods for robust time-reversal focusing in fluctuating ocean environments.
Main Methods:
- Analysis of experimental data from high-frequency transmissions.
- Numerical simulations to model acoustic wave propagation and focal intensity variations.
- Application of waveguide-invariant theory to understand focal shifts.
Main Results:
- Sound speed fluctuations due to internal waves induce phase changes in acoustic waves, causing focal shifts and intensity variations.
- Experimental and simulation results confirm the link between intensity variation and focal shift.
- Waveguide-invariant theory illustrates relationships between focal range shift, frequency shift, and channel depth.
Conclusions:
- Dynamic ocean environments significantly impact time-reversal focusing stability.
- Developed methods aim to enhance the duration of stable focusing by mitigating environmental effects.
- Understanding sound speed fluctuations is crucial for effective underwater acoustic focusing.