MODIFIED T-MATRIX FORMULATION FOR MULTIPLE-SCATTERING OF ACOUSTIC-WAVES

In studying the multiple scattering of acoustic waves by distributed d iscrete scatterers, the 'two-exterior' T-matrix or the modified T-matr ix is needed. In this paper, the modified T-matrix formulae for a scat terer of arbitrary shape are derived, based on Huygen's principle and the method of optimal truncation (MOOT), respectively. Analytical expr essions are given for the modified T-matrix elements of a spheroid in the low-frequency limit. The agreement with the existing results is sh own to be exact to the given order of ka. It is also shown that the re sults based on Huygen's principle are merely the special cases of thos e based on MOOT.