Using the trapped energy ratio for source depth discrimination with a horizontal line array: Theory and experimental...

Area of Science:

• Underwater acoustics
• Signal processing
• Oceanography

Background:

• Accurate acoustic source depth estimation is challenging in many underwater scenarios.
• Acoustic source depth discrimination offers a simplified binary classification (surface vs. submerged).
• Shallow water environments pose unique challenges for acoustic signal propagation.

Purpose of the Study:

• To introduce and validate a method for acoustic source depth discrimination.
• To assess the feasibility of classifying acoustic sources as near-surface or submerged.
• To evaluate the performance of the method under various conditions.

Main Methods:

• Utilizing signals from a horizontal line array in shallow water.
• Employing a normal-mode propagation model requiring prior knowledge of mode characteristics.
• Estimating the trapped energy ratio in mode space for classification.
• Performance prediction via simulations and Monte Carlo methods.
• Validation using experimental data from New Jersey coastal waters.

Main Results:

• The method successfully discriminates between surface and submerged acoustic sources.
• Performance is influenced by frequency, noise, array aperture, and environmental model accuracy.
• Numerical studies and experimental data confirm the approach's effectiveness.
• The impact of environmental model errors on performance was illustrated.

Conclusions:

• Acoustic source depth discrimination is a viable technique for basic source depth information.
• The normal-mode based approach using trapped energy ratio is effective in shallow water.
• The method demonstrates robustness and applicability to real-world underwater acoustic data.