### ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

## 5aUW4. Nonparabolic marching algorithm for sound field calculation in the
inhomogeneous ocean waveguide.

**A. Voronovich
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*NOAA/ERL/Environmental Technol. Lab., 325 Broadway, Boulder, CO 80303
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A new algorithm is proposed for calculating sound field in the
inhomogeneous ocean waveguide. It does not involve parabolic approximation and
at least for 2D inhomogeneities can be considered as exact. On the other hand,
it is ``marching'' and can be as easily implemented as a parabolic equation.
For inhomogeneity with final horizontal extent, the algorithm calculates, in
particular, the scattering matrix for acoustic modes interacting with
inhomogeneity. It is significant that the approach is able to calculate not
only the acoustic field itself, but propagation times of different modes as
well. The cases of uneven boundary and media with losses can be also dealt
with. Thus the algorithm is able to provide an exact solution of the Helmholtz
equation with 2D inhomogeneities both for shallow- and deep-water situations.
The algorithm can be easily generalized for the case of the moving media and/or
density variations. The corresponding code does not require great computer
memory or speed and can be performed on a conventional PC. Numerical
simulations of sound propagation through strong inhomogeneity related to
subpolar front will be presented. Two types of mode interaction appearing for
two-channel situations will be discussed. [Work supported by ONR.]