Estimation of the absorption performance of porous material/MPP compound structure

The model of the specific acoustic impedance of the porous material/MPP compound structure was established in this paper, and then the relations between the compound structure and the single absorbers were built based on the acoustic impedance model. Some qualitative conclusions were thereby gained through the analysis on the single structures, such as the compound structure and the micro-perforated panel absorber usually resonate at different frequency. All these conclusions were verified by the experimental results. Besides, it is very complicated to calculate the absorption coefficient of the compound structure directly, but predicting the absorption coefficient in low frequency range is very meaningful for the compound structure in engineering. Therefore, based on the theoretical and experimental research on the porous mate-rial/MPP compound structure, a model was proposed for predicting the absorption coefficient of the compound structure in low frequency range. According to the model, the absorption coefficient of the compound structure can be predicted by the absorption coefficients of the single structures, and the prediction of the absorption coefficient of the porous materials and micro-perforated panel absorbers are relatively simple. The prediction results and the measured results have a good agreement.