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

Abstract

Acoustic deficiencies due to lack of absorption in indoor spaces may sometime render significant buildings unfit for their purpose, especially the ones used as speech auditoria. This study investigates the potential of designing wideband acoustic absorbers composed of parallel-arranged micro-perforated panels (MPPs), known as efficient absorbers that do not need any other fibrous/porous material to have a high absorptive performance. It aims to integrate architectural trends such as transparency and the use of raw materials with acoustical constraints to ensure optimal indoor acoustic conditions. It proposes a structure composed of four parallel-arranged MPPs, which have been theoretically modelled using the electrical Equivalent Circuit Model (ECM) and implemented on an acrylic prototype using recent techniques such as CNC machining tools. The resulting samples are experimentally analysed for their absorption efficiency through the ISO-10534-2 method in an impedance tube. The results show that the prediction model and the experimental data are in good agreement. Afterward, the investigation focuses on applying the most absorptive MPP structure in a classroom without acoustic treatment through numerical simulations in ODEON 16 Acoustics Software. When the proposed material is installed as a wall panel, the results show an improvement toward optimum values in Reverberation Time (RT30) and Speech Transmission Index (STI).

Measurement of the absorption coefficient of inhomogeneous Micro-Perforated Panels in a Small-Scale Reverberation Room

“…The parameter values chosen for this study are based on the previous parametric analysis by the Equivalent Circuit Method [13] and concerned at the same time with manufacturing limitations (applicability). The material was assumed to be rigid so that it does not vibrate and has enough mechanical strength.…”

“…To broaden the absorption bandwidth, researchers have explored various structures based on MPP arrangements in series, parallel and combined, which by introducing multiple resonances yield efficient and wideband sound absorption [4][5][6]. Previous works by the authors [7] investigated the potential of transparent parallel arrangement of four MPPs in the impedance tube. Preliminary results have shown that a wider band and higher absorption can be achieved simultaneously by tuning each resonator to an overlapping resonance frequency with the precedent.…”

“…Preliminary results have shown that a wider band and higher absorption can be achieved simultaneously by tuning each resonator to an overlapping resonance frequency with the precedent. The proposed material was implemented in a simulated classroom setting and found that transparent MPPs could effectively absorb sound in the speech frequency range [7]. Literature shows that the models continue to develop in the field of engineering.…”