Sound absorption characteristics of a honeycomb-backed microperforated panel (MPP) absorber

Abstract

Microperforated panels (MPPs) are typically made of a thin metal or plastic panel and are often unsuitable for an interior finish because thin limp panels do not have enough strength. In particular, an interior finish of room walls requires appropriate strength. In order to solve this problem, a honeycomb structure is attached behind MPPs to stiffen the construction. Thus, it is possible to stiffen an MPP without increasing its thickness, which is important to keep MPPs at their best absorption performance. Furthermore, a honeycomb can increase MPPs’ absorption coefficient in a similar way as a porous layer backed by a honeycomb. In this study, an experiment was performed to gain insight into the acoustical effect of a honeycomb structure behind MPPs and a simple theoretical model to interpret the experimental effects is presented. The experimental results show that the honeycomb affects the absorption characteristics of MPPs: the absorption peak increases and shifts to lower frequencies. This effect becomes more significant as the thickness of the honeycomb increases. The results from the theoretical model show the same tendency. This is attributed to the fact that the honeycomb makes a similar condition to local reaction in the back cavity.