Acoustic Propagation and Source Characterization in Complex Marine Environments

Accurately modeling sound generation and propagation in the ocean environment is essential for applications such as sonar imaging, environmental noise prediction, and the design of low-noise platforms. In this study, we develop a unified, high-fidelity linear acoustics framework that integrates both steady-state and transient solvers to investigate complex marine acoustic environments involving turbulence, bubble plumes, compliant boundaries, and seabed structures such as sediment and biofilms. For steady-state fields, a validated boundary element method (BEM) solver resolves high-frequency signals (>100 kHz) with excellent numerical stability, enabling efficient modeling of sonar returns and detailed analysis of seabed reflectivity in layered or rough environments. To capture transient, broadband acoustic phenomena, we employ the modified finite-difference time-domain (MFDTD) method, which eliminates numerical artifacts caused by the discrete motion of sources or interfaces. This is achieved through smooth Hermite blending of boundary conditions across rasterized time windows, ensuring clean simulation of sound from moving sources, turbulent eddies, and vibrating surfaces. By exploiting the linearity of the wave equation, our computational framework decomposes the pressure field into distinct physical contributions, enabling the detailed isolation, interpretation, and, if desired, filtering of effects such as turbulence, bubble dynamics, and seabed complexity. This simulation tool enables both more accurate sonar-based mapping and deeper insight into underwater noise signatures, laying the foundation for predictive, multi-physics acoustics modeling in real-world marine environments.