Design of compact micro-perforated membrane absorbers for polycarbonate pane in automobile

Polycarbonate (PC) laminate is gradually substituted for the glass as window pane in automobile. Absorption performance of PC pane is poor using resin membrane between two folders of pane because of the low acoustic impedance of membrane. Micro-perforated absorbers can provide high absorption coefficients. However, the depths of air cavity were all over the 50 mm in past studies. In this paper, a compact and efficient micro-perforated membrane (MPM) absorber is designed as a combination of baffle-resonator and Helmholtz-resonator with sub-millimeter holes backed by an air space. Absorption coefficients of MPM absorbers are predicted by equivalent electric-acoustic circuit analysis method. This paper presents three different MPM materials of polypropylene, polyethylene, and carbon polyester respectively. The numerical results shows that absorption performance of PC pane can be improved using double layer MPM absorber and the whole thickness of MPM absorber is not exceed 10 mm to meet the structural requirement of PC pane application in automobile.