Abstract
Micro-perforated panels (MPPs) are one of the most promising alternatives to conventional porous sound-absorbing materials. Traditionally, the theory of the sound absorption properties of MPPs is based on the assumption that MPPs are a homogeneous material with identical pores at regular intervals. However, in recent years, some MPPs have not met these conditions, and although a variety of designs have been created, their properties and prediction methods were studied in only fewer works. In this paper, considering the wide variety of MPP designs, we made a trial production of heterogeneous MPPs, which are MPPs with holes of different diameters, and studied the prediction method applicable to these MPPs. We measured the normal incidence sound absorption characteristics of those MPPs, backed by a rigid backing and air-cavity in-between, in an impedance tube. The prediction method proposed in this work is to treat the heterogeneous MPPs as combinations of several homogeneous components, and to combine them after applying the existing theory on homogeneous MPPs to each component. As a result, except in a few cases, the measured and predicted values of the absorption properties agreed relatively well. We also found that the arrangement of the holes in the material and the depth of the back cavity affected the agreement between the measured and predicted results.
Highlights
Micro-perforated panels (MPPs) [1] have become widely known as one of the most promising alternatives to conventional porous absorbers due to their durability, hygiene benefit, recyclability, and designability.Maa [2,3] first studied the absorption structure of micro-perforated panels (MPPs) and proposed a prediction method for the absorption characteristics
These developments in research works, but recently there have been various new sound absorbing products using MPPs with sophisticated designs [9]. Another theory for designing the acoustical properties of MPPs, proposed by Guo et al [10], is considered to be useful: It is similar to Maa’s theory, but can include various resistive end correction treatments, and is applicable to holes with an arbitrary cross-sectional shape. Both Maa’s and Guo’s theories assume that MPPs have uniformly sized holes at a constant distance from each other, i.e., they assume homogeneous MPPs taking the average of the impedances of holes and non-hole parts
In ference in arrangement causes the difference in acoustic properties between these specimens
Summary
Micro-perforated panels (MPPs) [1] have become widely known as one of the most promising alternatives to conventional porous absorbers due to their durability, hygiene benefit, recyclability, and designability.Maa [2,3] first studied the absorption structure of MPPs and proposed a prediction method for the absorption characteristics. Since Maa’s pioneering works, there have been many studies on implementation [4,5,6], and various usage and applications have been comprehensively reviewed in [7,8] These developments in research works, but recently there have been various new sound absorbing products using MPPs with sophisticated designs [9]. Another theory for designing the acoustical properties of MPPs, proposed by Guo et al [10], is considered to be useful: It is similar to Maa’s theory, but can include various resistive end correction treatments, and is applicable to holes with an arbitrary cross-sectional shape. Both Maa’s and Guo’s theories assume that MPPs have uniformly sized holes at a constant distance from each other, i.e., they assume homogeneous MPPs taking the average of the impedances of holes and non-hole parts
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