Theoretical and Experimental Study on Sound Absorption of a Multi-leaf Microperforated Panel

A theoretical method is presented for calculating the absorption coefficient of a multi-leaf microperforated panel absorber. In this work, the possibility of using multi-leaf type of microperforated panels without solid backing panel is investigated. The number of panels varies from 2 to n (≥2). The sound absorption coefficient is calculated based on electro-acoustic analogy by taking the sound transmission coefficient due to the absence of solid backing panel into consideration. The optimum performance of leaf microperforated panel absorber is also investigated as the function with respect to the design parameters such as perforation ratio, diameter of holes and distance between panels. The numerical results show that the configuration of leaf of microperforated panels can increase absorption coefficient at low frequency region. This fact will give an advantage to the multi-leaf microperforated panel over conventional microperforated panel arrangements. That is, to solve the problem of quite narrow frequency band absorption effect, especially in mid-high frequency region corresponding to their resonant frequencies, that the conventional microperforated panel arrangements inherently possess. Experiment results are also presented that show a reasonable agreement with the theoretical results. Some feasible application ideas of the multi-leaf type of arrangement are also presented.