Through the sensor estimation of sound speed profiles

Area of Science:

• Oceanography
• Acoustics
• Signal Processing

Background:

• Ocean sound speed profiles (SSP) are crucial for underwater acoustic propagation.
• Traditional methods for SSP measurement can be complex and resource-intensive.
• Ocean acoustic energy propagates as discrete modes within the water column.

Purpose of the Study:

• To propose a through-the-sensor method for sensing the local sound speed profile (SSP).
• To utilize measured acoustic wave numbers from hydrophone arrays for SSP inversion.
• To exploit environmental information from in situ sonar systems.

Main Methods:

• Formulating a Fredholm integral equation of the first kind to relate sound speed corrections to wave number differences.
• Employing sparse inversion techniques for robust SSP estimates, even with limited prior information.
• Utilizing an iterative algorithm with multiple acoustic frequencies for stability and convergence.
• Comparing broadband incoherent L2- and coherent L1-inversion methods.

Main Results:

• Demonstrated the feasibility of the through-the-sensor method via simulations.
• Validated the approach using data from the Littoral Depth Discrimination Experiment 2012 (LIDDEX12).
• Showcased the potential for stable and accurate SSP estimation with sparse inversion improvements.

Conclusions:

• The proposed method provides a viable approach for in situ SSP determination.
• Iterative algorithms and sparse inversions enhance the robustness of acoustic inversions.
• Careful selection of acoustic frequency, modes, and array parameters is essential for optimal performance.