Acoustic measurement of a 3D printed micro-perforated panel combined with a porous material

The sound absorption coefficient of a micro-perforated panel (MPP) backed by a porous sound absorbing material is investigated in this paper. The feasibility to fabricate an MPP acoustic absorber using 3D printing technology is presented. The test specimens are made of polymer material, and they are printed with different perforation ratios. A porous sound absorbing material is added to the MPP samples to form an acoustic absorber structure. Their sound absorption coefficient is experimentally measured by using the impedance tube method. The results obtained are theoretically validated by using the transfer matrix method (TMM). The MPP is modelled using Maa's method, and the equivalent fluid model is used to calculate the acoustic property of the porous sound absorbing material layer. The results show that the sound absorption coefficient of a 3D printed MPP backed by a porous sound absorbing material agrees fairly well with the theoretical model. By adjusting the perforation ratio, MPP acoustic absorbers with high absorption peaks can be implemented. The results in this paper provide a new approach for fabricating MPP sound absorbers for acoustic applications. (C) 2017 Elsevier Ltd. All rights reserved.