NUMERICAL-SOLUTION OF THE COUPLED-MODE EQUATIONS IN DUCT ACOUSTICS

We present a fast solver for the coupled mode equations in duct acoust ics. It is based on a partitioning of the resulting system of ordinary differential equations into separate subsystems, the number of which increases by the separability of the problem. This structure is obtain ed by transformations of the dependent variables such that weakly inte racting modes are separated. The decoupling process requires the numer ical solution of algebraic Riccati equations. However, these computati ons can be done on a spatial scale much larger than the characteristic wavelength of the problem. (C) 1994 Academic Press, Inc.