A PRACTICAL APPLICATION OF THE GALERKIN METHOD TO THE BROAD-BAND CALCULATION OF NORMAL-MODES FOR UNDERWATER ACOUSTICS

A new application of the Galerkin technique to the calculation of the normal modes that are used to describe underwater acoustic propagation is presented. This expansion approximation method (EAM) is especially relevant for broadband normal mode calculations in which normal mode eigenvalues, depth functions, and attenuations are needed. The EAM is used to construct approximate normal mode eigenvalues and depth functions for some frequency from eigenvalues and depth functions previously calculated at another, higher frequency. The EAM approach for broadband underwater acoustic propagation calculations is evaluated in comparison with an exact normal mode model calculation of impulse responses and other broadband results. (C) 1995 Acoustical Society of America.