Passive source depth estimation without prior sound speed profile in reliable acoustic path environments

Area of Science:

• Oceanography
• Acoustics
• Signal Processing

Background:

• Underwater acoustic environments are often dominated by direct (D) and surface-reflected (SR) paths.
• Estimating source depth relies on the time delay between D and SR paths, but is sensitive to sound speed profile (SSP) variations.

Purpose of the Study:

• To develop a robust method for underwater source depth estimation.
• To address and mitigate the performance degradation caused by SSP mismatches.

Main Methods:

• Theoretically demonstrated a linear relationship between D-SR time delay, source depth, and an SSP nuisance term.
• Reformulated source depth estimation as a linear model coefficient estimation problem.
• Applied least squares methods for a closed-form solution, termed the joint sound-speed and source depth estimator.

Main Results:

• The proposed method accurately estimates source depth without requiring prior SSP knowledge.
• Demonstrated robustness against SSP mismatches through simulations.
• Validated effectiveness using real experimental data from the Western Pacific.

Conclusions:

• The joint sound-speed and source depth estimator provides accurate and rapid underwater source depth estimation.
• The method offers improved robustness compared to existing techniques, especially under SSP variations.
• Successful real-world application confirms its practical utility in underwater acoustics.