Effect of mean flow and damping on the performance of reactive mufflers

Inclusion of mean flow effects in the mathematical modeling of exhaust mufflers has been found to be essential for achieving realistic results. Two mathematical models are presented which apply to plane wave propagation through a pipe or an expansion chamber including the effect of mean flow and damping. The solutions of the governing equations are represented by 2×2 transfer matrices. In evaluating the performance of exhaust mufflers, noise reduction (NR) is calculated using an open end termination. The measured NR characteristics of the tested laboratory mufflers are in excellent agreement with those predicted by the transfer matrix approach. The method of NR calculation is quite general in its application and can be extended further to optimize muffler configuration at the design stage