Effect of honeycomb structure in the back cavity on the absorption characteristics of microperforated panel absorbers

Since the principle of microperforated panel absorbers (MPPs) was established, many studies have been made on their practical applications. MPPs are typically made of very thin metal or plastic panels to obtain high absorption. However, such a thin, limp panel is in many cases not suitable for an interior finish of room walls because of its insufficient strength. The authors have proposed to use a honeycomb structure attached behind an MPP to stiffen it without deteriorating its acoustical performance. The honeycomb behind an MPP can also be expected to enhance its absorption performance, considering previous studies on porous sound-absorbing layers with the back cavity completely partitioned by a honeycomb structure. In this paper, the effect of honeycomb structure in the back cavity on the absorption coefficient of MPP was experimentally studied. The results suggest that the reverberation sound absorption characteristics become close to those of an MPP without a honeycomb structure for normal incidence. This means that the characteristics are improved with the honeycomb structure to show a higher and broader absorption peak. MPPs can be used more efficiently in more various situations with applying elaborated configurations of backing structures. [Work supported by the Kajima Foundationfs Research Grant.]