Analysis of the noise attenuation in ducts by means of rigid perforated panels

The noise of Heating, Ventilating and Air Conditioning (HVAC) systems is an important aspect to take into account when the comfort of the users is compromised. For instance, passengers in trains perceive this noise, which influences the perception of the quality of the travel. Therefore, solutions to attenuate that noise need to be proposed and applied. In this work, analytical models of the sound transmission in ducts through rigid perforated panels are applied and the results are validated according to Finite Element calculations. By means of these analytical models, the acoustic propagation behaviour is understood and the influence of the geometry of the perforated panels is analysed. The effect of the shape of the perforations is compared for circular and square perforations. The effect of the size of the perforations and the distance between them are also analysed. It is observed, that changing those parameters of the rigid perforated panels, significant improvements in the transmission loss can be achieved and that the analytical models are a useful tool to understand and improve the acoustic behaviour.