Acoustic wave propagation in underwater shallow channel environments

Previous attempts to model acoustic propagation in a shallow underwater channel using transmission line matrix (TLM) have been hampered by shortfalls in the basic formulation of an otherwise competent numerical modelling technique. Significant advances have been made in recent years and it is now possible to demonstrate the benefits of TLM in this application. Perfectly matched boundaries to limit the computation size to a specific area of interest are one of these advances. After introducing details of the TLM method we proceed to model a number of scenarios which describe acoustic propagation in an open finite channel of ocean. We confirm the need for an accurate boundary-conforming description and demonstrate why mesh refinement strategies are not appealing in this situation. Our approach can be used to account for the distortions in the received signal in an underwater channel and we highlight the influence of both surface state and receiver position.