Passive geoacoustic inversion with a single hydrophone using broadband ship noise

Area of Science:

• Ocean acoustics
• Geophysics
• Signal processing

Background:

• Underwater acoustic measurements are crucial for understanding ocean environments.
• Analyzing ambient noise provides a unique approach to characterizing the seabed.

Purpose of the Study:

• To develop and validate an inversion scheme for estimating geoacoustic properties using noise from a moving ship.
• To assess the method's performance with varying signal-to-noise ratios and its applicability to multi-layer bottoms.

Main Methods:

• Utilizing noise spectrograms from a single hydrophone to identify modal striations.
• Estimating radial wavenumber differences and stacking them to form relative dispersion curves.
• Inverting these curves against a propagation model to determine bottom geoacoustic parameters.

Main Results:

• A minimum 6 dB signal-to-noise ratio is needed for unbiased compressional sound speed estimation with a 3 m/s standard deviation.
• Estimation error remains bounded even at lower signal-to-noise ratios.
• The scheme successfully estimates a depth-averaged compressional sound speed for multi-layer bottoms.

Conclusions:

• The proposed inversion scheme is effective for characterizing ocean bottom geoacoustic properties.
• The method demonstrates robustness across different signal-to-noise conditions.
• Experimental results align with direct core sample measurements, validating the technique.