A finite element model to predict sound attenuation in lined and parallel-baffle rectangular ducts

The present article describes a Finite Element Model (FEM) model for the analysis of sound attenuation in lined and parallel-baffle rectangular ducts. By means of the numerical model it was possible to predict insertion losses in a frequency range up to 8000 Hz. The model was validated by comparing numerical results with experimental data obtained in accordance to EN ISO 11691 and EN ISO 7235 standards. For the lined ducts both lining thickness and physical properties of lining were varied during validation; the comparison indicates a good accuracy of the numerical model for all different tested conditions. The results of the validation for parallel-baffle rectangular ducts show that also the behaviour of these dissipative/reactive silencers, with their internal-reflections and energy dissipation phenomena, can be predicted quite well by the FEM model on the whole frequency range. Overall comparisons suggest that FEM modelling can be an accurate and inexpensive way to predict sound attenuation in lined ducts and parallel-baffle mufflers.