4-D modeling of sound propagation in shallow water with anisotropic sediment layers

Abstract

A highly efficient 4-D PE model is developed to study broadband sound propagation at the Atlantic Generating Station (AGS) site. Extensive core data has shown that the sediment at this AGS site consists of multiple layers which vary in both range and azimuth. Consequently, sound propagation in the water column in this area is significantly affected by the complex sediment structure due to the fact that the layered sediment acts like a bandpass filter in which broadband acoustic energy is selectively broken into narrow-band components propagating in different layers, usually referred as sediment mode trapping. The details of the range, azimuth, frequency, and bandwidth dependences as well as their relationships to the sediment structure of such mode trapping effect is numerically explored by performing the 4-D PE model. The empirical orthogonal function representation method is employed to transfer the geoacoustic parameters of the sediment core data into PE inputs. The broadband travel time results at eight different bearings are compared with the existing experimental data. The importance of the 3-D effects is also examined by comparing the numerical results of azimuthal coupled and uncoupled models.