Noise attenuation prediction and analysis in rectangular lined ducts

Abstract

The noise of Heating, Ventilating and Air Conditioning (HVAC) systems is an important aspect when the comfort of the users is compromised. Thus, solutions to attenuate that noise need to be proposed. Linings in ducts are the main noise absorption method, and therefore, their design optimised. Finite element models predict the behaviour of these systems accurately, but high frequency ranges in long ducts become a challenge due to computational requirements. So, analytical models are preferred for optimisations. In this work, analytical models of the sound transmission in lined ducts are presented and the results are validated in accordance with Finite Element calculations. Symmetrical and asymmetrical linings are considered and it is shown how the optimum lining can be determined in each case. With symmetrical or asymmetrical linings the modes contributing to the propagation change, and thus, the resultant noise absorption changes. Results show that at lower frequencies the asymmetrical linings can improve the sound attenuation.