Effects of three-dimensional modes on acoustic performance of reversal flow mufflers with rectangular cross-section

Acoustic performance of reversal flow mufflers in a stationary medium is analyzed using Munjal’s numerical approach as well as the three-point method. Three-dimensional modes and their associated frequencies are discussed with respect to the transmission loss of the muffler. Computed values of transmission loss are compared with those obtained by the indirect boundary element method. Numerical results show that the values of transmission loss drop to zero or to the minimum at the frequencies when those modes are excited.