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Virtual head waves in ocean ambient noise: Theory and modeling
Jie Li1, Peter Gerstoft2, Martin Siderius3
1Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
The Journal of the Acoustical Society of America
|December 31, 2020
Summary
This study extracts virtual head waves from ocean ambient noise, revealing their potential for seabed parameter estimation. These waves, often overlooked, offer new insights into underwater environments.
Area of Science:
- Acoustics
- Geophysics
- Oceanography
Background:
- Traditional Green's function retrieval methods in horizontally bounded media focus on direct and reflected waves.
- Virtual head waves, observed in ocean ambient noise, are experimentally utilized for environmental and geometric parameter inversion.
- Ocean ambient noise comprises direct, reflected, and head waves, with virtual head waves arising from their cross-correlations.
Purpose of the Study:
- To derive the extraction of virtual head waves from ocean ambient noise within a Pekeris waveguide.
- To demonstrate the estimation of seabed sound speed using virtual head waves and a vertical line array.
- To investigate the observability and characteristics of virtual head waves for geophysical applications.
Main Methods:
- Utilizing a vertically spaced sensor pair to analyze ocean ambient noise.
- Applying the method of stationary phase to determine the locations of virtual head wave sources.
- Employing cross-correlation techniques to identify and isolate virtual head waves from other wave components.
Main Results:
- Virtual head waves are successfully extracted from ocean ambient noise.
- The method allows for the estimation of seabed sound speed using these virtual head waves.
- Distinct slopes of virtual head waves in virtual source gathers enable constructive stacking and improved signal retrieval.
Conclusions:
- Virtual head waves are a significant, yet often ignored, component of ocean ambient noise.
- Their extraction and analysis provide a viable method for estimating seabed acoustic properties.
- This technique enhances geophysical inversion capabilities in marine environments.
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