Coupled perturbed mode method and solitary internal wave

In shallow water environment, sound propagation through internal solitary waves involves mode coupling. The local normal modes in range-dependent environment can be found using a perturbation method developed by Higham and Tindle, which yields accurate and fast normal mode solutions when combined with coupled-mode theory. The method of Higham and Tindle is limited to low frequency (≤ 400 Hz). In order to increase the work frequency of the perturbation method in solitary internal wave environment, we keeping the high-order terms in the perturbation method and using the iteration algorithm, so we get the more accurate local normal modes, and also increase the work frequency of this computation method for sound waves to 3 kHz. The approach has been verified in internal solitary wave packet environment