Time-evolving three-dimensional (four-dimensional) numerical modeling of sound is performed for ocean environmental conditions calculated using regional ocean flow models. The flow models solve the appropriate nonlinear equations in bands of resolved scales and frequencies. Subgrid scale processes are parameterized, as are boundary processes. The ocean fields are interpolated onto acoustic model grids that are two orders of magnitude tighter than the flow model grids. The computations provide reliable estimates of the acoustic effects of the resolved ocean processes such as geostrophic currents, mixed-layer changes, and internal tides, but they do not include the acoustic implications of unresolved structures such as nonlinear internal waves, sharp boundary layers, and small-scale intrusions. Examples of complicated sound fields from resolved and unresolved features will be presented, and prospects for applying the methods will be discussed
