A note on the coupling mechanism of micro-perforated panel absorber

Extensive research was found in the literature regarding to the topic of Micro-perforated Panel Absorber (MPA). However, these works mainly focused on examining the performance of this device. As a result, the coupling mechanism of the MPA system is less highlighted. Conventionally, MPA was recognized as a local reactive sound absorption material, that its property is spatially independent over the panel surface. But in fact, a Micro-perforated Panel (MPP) with the backing cavity forms a coupling system and its absorption capability is determined by the coupling between the MPP and the backing cavity modes. Depending on the type of the cavity modes that dominate in the coupling, the MPA may be either local reactive or not. For the latter case, the horizontal modes dominate in the coupling and the non-local reactive property of the MPA varies with respect to the dimension of the MPP. This usually results local absorption performance variation, leading to global performance degradation. As a solution, it is suggested to use partitioned backing cavities so that the original non-local reactive absorption material becomes local reactive. If the partitioned backing cavities with different depths are used, it is possible to further enhance absorption performance of MPA.