High frequency normal mode statistics in a shallow water waveguide: the effect of random linear internal waves

Area of Science:

• Underwater acoustics
• Ocean acoustics
• Wave propagation

Background:

• Shallow water environments exhibit complex sound propagation due to random sound-speed perturbations from internal waves.
• Statistical properties of acoustic mode propagation are crucial for understanding underwater sound fields.

Purpose of the Study:

• To investigate the statistical properties of acoustic mode propagation at 1 kHz in a shallow water environment with internal wave-induced sound-speed variations.
• To develop and validate a computationally efficient transport theory for modeling mode propagation under these conditions.

Main Methods:

• Utilized transport theory and Monte Carlo numerical simulations.
• Analyzed statistical properties including second and fourth moments of mode amplitudes.
• Developed a hybrid transport theory incorporating adiabatic cross-mode correlation and mode coupling.

Main Results:

• Mode phase randomization exhibits a strong adiabatic component, alongside significant mode coupling rates.
• The hybrid transport theory accurately reproduces statistical quantities from Monte Carlo simulations.
• The theory includes closed-form expressions for the internal wave scattering matrix and an edge effect correction.

Conclusions:

• The developed hybrid transport theory provides an accurate and efficient method for modeling acoustic mode propagation in shallow water with internal waves.
• The findings contribute to a better understanding of sound intensity and scintillation in dynamic ocean environments.