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Comparison of Sound Pressure in a Wedge-Shaped Ocean as Predicted by an Image Method and a PE Model

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Master's thesis

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We compare and contrast results of three different models of acoustic propagation in an ocean with a sloping bottom, predicting the pressure field in a wedge-shaped ocean with a pressure release surface and an acoustically fast bottom. On image and two PE Parabolic Equation models were selected. The computer model for the image method was written in Basic for use on a PC and in Fortran for use on the NPS IBM 3033 computer main frame. The geometric shape of the wedge for the image calculation consists of a plane, sloping penetrable bottom and a plane, horizontal pressure release upper surface. This shape models a real continental shelf. The shape used in a parabolic equation models is a pressure release plane surface above the conical bottom. Two PE models were studied. One is based on a wide angle parabolic equation and providing a contour plot of TL as a function of position. The other, resident on the NPS computer, is based on an implicit finite difference algorithm. Results show that there is fair agreement among the different models. Comparison of the image method and the second PE model show a 2 to 3 dB difference in transmission loss near the surface and good agreement deeper. The transmission loss predicted by the first PE model differs from both other models by 4 to 5 dB near the surface and at the middle depths. Near the bottom they all agree well.

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  • Physical and Dynamic Oceanography
  • Acoustics

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