Simulation of acoustic performance of mufflers and silencers using spectral element methods

Acoustic fields inside mufflers and silencers have been simulated to predict their effectiveness as noise control devices. Transmission loss, which is the difference between the input and the output sound pressure level at a certain frequency, is considered as an important measure for the effectiveness of such noise control devices. Therefore, its accurate and efficient calculation for a range of frequencies has been the main focus of this work.;A three-dimensional spectral element method has been developed to simulate linear time-harmonic acoustic wave propagation, governed by Helmholtz's equation, in closed domains. The effect of convection due to mean flow has been neglected for simplicity.;For solving wave propagation problems, a minimum number of degrees of freedom per wavelength for each spatial dimension must be maintained to ensure a reliable solution. Higher-order elements are more accurate, and therefore require less number of degrees of freedom per wavelength. The computational performance of spectral element methods for Helmholtz's equation has been studied. Moreover, parallel processing on a cluster of distributed-memory machines has been implemented for large problems that can not be solved using only one processor.;The method has been successfully applied to simulate the acoustic field inside mufflers and silencers with absorption material (porous medium) and perforated plates. The accuracy of the results has been evaluated by comparing the predicted values with the available measured values of the transmission loss for the frequency range of interest. Good agreement has been observed.