Sound attenuation using duct silencers with micro-perforated panel absorbers

Micro-perforated panel (MPP) can be used as non-fibrous acoustic absorber which can provide broadband sound absorption performance. In this study, a sub-structuring methodology based on the Patch Transfer Function (PTF) approach to deal with duct silencers with MPP absorbers and internal partitions is proposed, and the sound attenuation performance of such silencers is investigated. Reactive silencers with only internal partitions are shown to exhibit strong resonant pattern, with each sub-divided chamber acting as acoustic resonators for strong sound reflection. On the other hand, hybrid silencers which combine the reactive effect of partitions and dissipative effect of MPP absorbers are studied. Simulation results show that MPP parameters such as hole diameters have strong influence on the silencing performance. Although the hole diameter of MPP is typically very small (less than 1mm), the reactive effect of MPP silencer is still obvious. The calculation accuracy of the proposed formulation is validated against finite element method (FEM) analysis.