A Basic Study on the Absorption Properties and Their Prediction of Heterogeneous Micro-Perforated Panels: A Case Study of Micro-Perforated Panels with Heterogeneous Hole Size and Perforation Ratio

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.

Acoustic Applications of a Foamed Geopolymeric-Architected Metamaterial

“…At higher frequencies, the perforated sample surpasses the solid sample, reaching higher sound absorption coefficient values (SAC) values. This trend can be elucidated by the perforations' capacity [77,78] to introduce acou tic impedance mismatches, leading to increased sound absorption efficiency at higher f quencies. The perforations likely contribute to dissipating sound energy effectively in t frequency range, demonstrating their advantage over the solid counterpart [85,86].…”

“…Accurate and reliable measurements are essential for designing spaces with optimal acoustic conditions. One widely accepted method for determining sound absorption coefficients is the impedance tube, which has proven effective in various applications using perforated panels [77,78]. This is the case of our samples consisting of perforated geopolymeric ceramic foams.…”

Investigating the Potential of Transparent Parallel-Arranged Micro-Perforated Panels (MPPs) as Sound Absorbers in Classrooms

“…Another interesting trail to follow in further work from the design perspective might be surface design in terms of visual patterns. This approach would behave as a trade-off between visual aesthetics and functional acoustics, which studies have attempted to achieve lately [61][62][63][64].…”

Sustainable Perforated Acoustic Wooden Panels Designed Using Third-Degree-of-Freedom Bezier Curves with Broadband Sound Absorption Coefficients

“…Advanced shapes in perforated panel materials are uncommon [ 6 ] as their performance is difficult to predict, while the high prototyping costs make the final reverberation chamber product testing unprofitable. Most of the current papers on acoustic panel development only cover the analytical problem formulation [ 7 , 8 ] or the final design measurement in the engineering reports [ 9 , 10 , 11 ].…”