Geometric sensitivity of frequency spreading due to acoustic scattering from wind driven water surfaces

Several recent studies have focused on the degree to which acoustic scattering from wind driven water surfaces exhibits frequency spreading which is asymmetric in any regular way. Ocean experiments, physical model studies and analytical models have so far not been entirely in agreement on this issue. Therefore a set of physical model experiments has been performed to investigate the sensitivity of frequency spreading asymmetries to variations in geometric parameters. These experiments were conducted using broadband probing signals in the model tank at Yale. Grazing angle, azimuth, projector and receiver beam pattern, acoustic frequency, and surface roughness were varied in a systematic way. The results of this series indicate that frequency spreading is in fact quite sensitive to a number of geometric parameters and that most current analytical models are inadequate to explain the detailed behavior of this phenomenon. [Work supported by NSF and Code 320, Naval Electronic Systems Command.]