Abstract:

Ambient noise due to surf has recently been empirically characterized as a source level density (SLD) per meter of beach as a function of wave height and frequency [Wilson et al., IEEE J. Ocean Eng. 22, 425--433 (1997) and J. P. Fabre and J. H. Wilson, IEEE J. Ocean Eng. 22, 434--444 (1997)]. Surf noise depends upon both the source level characteristics of different surf types and the unique propagation conditions from the surf zone seaward. This dependence must be examined in order to develop models capable of providing accurate ambient noise levels in shallow water. An inverse method for determining ambient noise due to surf as a function of beach slope, sediment type, wave type, as well as frequency and wave height is presented. Discussions of incorporating the Navy Surf model into this surf noise prediction method are also provided. A long-term ambient noise data set will be used to validate the method for various environmental scenarios at one location. Using data from other locations, results can be extrapolated to give preliminary estimates of bathymetric and geologic dependencies. The surf SLD as a function of surf type, etc., can be used for any shoreline. This makes it possible to use this model as an inverse noise model to estimate surf conditions on a beach remotely from noise measurements taken offshore.