Theoretical and numerical modelling of a parallel-baffle rectangular duct

Abstract

The paper describes the theoretical and numerical analysis of sound attenuation in a parallel-baffle rectangular duct. Insertion losses in a frequency range up to 8000 Hz were predicted by means of a FEM numerical model and by means of analytical models from Sabine and Kurze. The models were then validated in the frequency range from 125 to 8000 Hz by comparing theoretical and numerical results with experimental data obtained in accordance to EN ISO 11691 and EN ISO 7235 standards. The results of the comparison indicate that the behavior of such a dissipative/reactive silencer, with its internal-reflections and energy dissipation phenomena, can be predicted quite well by the FEM model on the whole frequency range. On the contrary, analytical models show little accuracy and such predictions are not always so accurate as design requires; besides, the complexity of the analytical approach tends to limit its application to the common design practice. Overall comparisons suggest that FEM modeling can be an accurate and inexpensive way to predict sound attenuation in parallel-baffle mufflers and fulfill the ever rising needs of proper methods in acoustic design of AC and ventilation plants. © 2012 Acoustical Society of America.