Underwater target depth estimation: A shallow-water broadband acoustic source depth estimation method based on...

Area of Science:

• Ocean Acoustics
• Signal Processing
• Underwater Localization

Background:

• Traditional methods for sound source depth estimation struggle in shallow seas with variable sound speed profiles.
• Existing techniques like the Warping transform are limited by assumptions of ideal waveguides.

Purpose of the Study:

• To propose a robust broadband sound source depth estimation method for shallow marine environments with non-ideal conditions.
• To address the limitations of traditional methods in handling variable sound speed profiles.

Main Methods:

• A modified Warping transform (MWT) operator was developed to compensate for signal propagation and reflection phases.
• Time-frequency analysis (TFR) was used to project modified signals, achieving clear mode separation.
• Modal energies were extracted and used to construct a depth estimation function.

Main Results:

• The MWT demonstrated superior mode separation in time-frequency domains compared to STFT and DDT under variable sound speed profiles.
• The proposed method achieved over 95% success rate for target depth estimation at a 10 dB SNR in various waveguide conditions.
• Accurate depth estimation was achieved in real sea experiments, separating normal modes and localizing an airgun pulse source.

Conclusions:

• The modified Warping transform method effectively resolves passive source depth estimation challenges in non-ideal waveguides with variable sound speeds.
• The proposed technique offers a wider application range and greater practical engineering value than traditional Warping transform methods.