J. Newcomb
Naval Res. Lab., SSC, MS 39529-5004
The ambient noise field is a complex and highly variable phenomena with many components, including contributions due to shipping. Spatial characteristics (e.g., the horizontal directionality) of the ambient noise field have been measured with towed line arrays in many of the major water masses of the world. This paper will address the effects of bathymetry on the propagation and measurement of ambient noise. It is shown that, in many cases, the horizontal directionality of the ambient noise can be fully understood only when the bathymetry along the propagation paths has been considered. Examples of measured data will be presented illustrating the effects of bathymetric stripping and bathymetric shielding on the spatial character of the ambient noise. Other examples of measured data will be shown demonstrating that bathymetric influences are not limited to a narrow frequency range. In addition, modeled data will be used to illustrate the effects of the surrounding bathymetry on noise and signal propagation. [Work supported by the Office of Naval Research (ONR) and the ASW Environmental Acoustic Support (AEAS) Project.]