Finite Element Acoustical Analysis of Complex Muffler Systems With and Without Wall Vibrations

Abstract

Typical exhaust muffler components, comprised of a flow-reversing chamber and a Helmholtz resonator, were studied. Results showed that the fundamental and higher resonance frequencies of Helmholtz resonators can be predicted accurately. The overall attenuation is sensitive to the location of the resonator throat connecting the flow-reversing chamber and the Helmholtz resonator, both at and off the resonance frequencies. The attenuation characteristics of several complete mufflers, composed of double reversing chamber and resonator combinations, were studied by the cascade connection of the four-pole transmission matrix for each component. The results were compared with those measured with and without steady mean flow. The finite element method developed in connection with the analogous acoustical transmission line theory has been demonstrated to be capable of modeling, with flexibility and accuracy, complex reactive-type muffler systems with and without wall vibration.