Research On Methods For Calculation Of Acoustic Field With Elastic Bottom Based On Parabolic Equation

In order to research the influence of elastic bottom on sound propagation in shallow water, an acoustic propagation model employing coordinate mapping approach, which is applied to slope elastic bottom depending on the range, based on parabolic approximation method, has been established. And a multi-grid parabolic equation method that can solve problems with low shear wave velocity is also given in this paper.Through the analysis of simulation in different environments, the parabolic equation method of coordinate mapping can be used to calculate acoustic field in middle and long distance at low or very low frequency with elastic bottom, which has very high accuracy. The coordinate mapping approach is more accurate than the rotated parabolic equation method for the filed with irregular elastic bottom. Multi-grid parabolic equation method overcomes the disadvantage of low efficiency of uniform grid method. The feasibility of coordinate mapping approach is verified by the fact that TL curves of sound propagation measurement agree well with that of the theory at low-frequency with elastic bottom. When the horizontal azimuth angle is very small, the 3-D effect is not apparent. While its value is very large,3-D effect becomes obvious because of the different acoustic propagation loss. Analysis of the structure of multi-path in the process of experiments is conducted to prove the validity of low-frequency acoustic propagation experiment.