Acoustic interferometry for geoacoustic characterization in a soft-layered sediment environment

Area of Science:

• Ocean acoustics
• Geophysics
• Environmental acoustics

Background:

• Moving ships generate broadband spectrograms with striations.
• Striation patterns in shallow water waveguides depend on seabed conditions.
• Seabed properties influence acoustic wave propagation and can be used for environmental characterization.

Purpose of the Study:

• To propose and validate a two-step acoustic interferometry technique for estimating geoacoustic properties of unconsolidated sediments.
• To utilize local features of ship noise striations for environmental characterization.
• To refine geoacoustic property estimation using low and high-frequency striation analysis.

Main Methods:

• A two-step acoustic interferometry approach is employed.
• Low-frequency striation positions are used to detect sediment property changes and estimate frequency shifts.
• High-frequency salient striations are analyzed for refined geoacoustic property estimation.

Main Results:

• The technique successfully estimated sediment thickness and compression wave speed in a clay layer overlying a harder bottom.
• Results from passive acoustic ship run data collected in the Mediterranean Sea showed good agreement with active inversion and seismic profiles.
• Combining results from multiple receivers improved resolution and demonstrated robustness to source range variations.

Conclusions:

• The proposed acoustic interferometry technique is effective for characterizing shallow water geoacoustic properties.
• The method is robust to source range uncertainties, making it reliable for practical applications.
• This technique offers a valuable tool for mapping coastal geoacoustic properties using simple receiver systems.