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

Abstract

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.

The sound absorption properties of a double-leaf micro perforated panel (DL-MPP) made from a double-layered polypropylene material.

“…Typically, an MPP is positioned with a rigid back wall behind it, creating an air cavity in between. The MPP sound absorber applies the same principle as a Helmholtz resonator, where the sound absorption mechanism primarily relies on the micro-perforations and the resonance phenomenon [2,3].…”

Relationship between Helmholtz-resonance absorption and panel-type absorption in finite flexible microperforated-panel absorbers

“…This type of absorption is mainly due to frictional loss in the air flow of the apertures. Various types of MPP structures have been proposed to improve the absorption characteristics [7][8][9][10][11][12][13]. Besides, the sound-induced vibration of an MPP itself also affects the absorption characteristics and there have been some studies considering such a vibration [14][15][16].…”