BEM analysis of exhaust network systems using the impedance matrix synthesis

A so-called impedance matrix synthesis (IMS) approach is used to replace the conventional four-pole transfer matrix for evaluating the transmission loss (TL) of exhaust systems. Unlike the four-pole transfer matrix, the impedance matrix is well defined for systems with multiple inlets and multiple outlets. More importantly, it is ideally suited to the boundary element method (BEM) because only one boundary element matrix needs to be solved at each frequency, regardless of the number of inlets and outlets. For a large network system with multiply connected subsystems, the resultant impedance matrix for the entire system can be easily obtained from the subsystem impedance matrices via the IMS operation. Also the transmission loss (TL) can be directly evaluated from the resultant impedance matrix. Numerical test cases with experimental verifications are given to demonstrate the IMS approach.