The solution of the reduced scalar wave equation for an almost stratified medium is written in the form of an asymptotic power series. The vertical structure of the solution is expressed as a linear combination of the normal-mode eigenfunctions whose coefficients satisfy two-dimensional eikonal and transport equations. Although smooth caustics may be treated for the two-dimensional scalar wave equation, the problem of a uniform approximation near a point source has not yet been resolved. Finally, the theory is applied to acoustic propagation in a realistic model ocean and the results are compared with measurements.
An acoustical propagation model was developed to analyze high-frequency propagation loss under shallow-water conditions. The model is based on Gaussian ray bundles which are similar in form but somewhat simpler than Gaussian beams. After describing the approach, propagation loss predictions are compared with those of various ‘‘standard models’’ at lower frequencies where the latter models are accurate and efficient. If Gaussian ray bundles compare well at the lower frequencies, they should perform well at the higher frequencies as ray approximations improve.
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