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. 2023 Jan 13;20(2):1445.
doi: 10.3390/ijerph20021445.

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

Ela Fasllija  1 , Semiha Yilmazer  1
Affiliations

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

Ela Fasllija et al. Int J Environ Res Public Health. .

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).

Keywords: acoustic comfort; micro-perforated panels; resonators; reverberation time; sound-absorbing materials; speech intelligibility.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) An MPP and its geometrical parameter and (b) its equivalent circuit.
Figure 2
Figure 2
(a) A schematic diagram of four parallel-arranged MPPs with partitioned cavities and (b) its respective equivalent circuit.
Figure 3
Figure 3
(a) Two layers of parallel-arranged MPPs with different back cavities. (b) The respective equivalent circuits of two layers of parallel-arranged MPPs with different back cavities after each layer.
Figure 4
Figure 4
(a) Acrylic prototypes; (b) CNC machining tools etching the back cavity structure; (c) Prototype 1—One-layer parallel-arranged MPPs; (d) Prototype 2—Double-layer parallel-arranged MPPs.
Figure 5
Figure 5
Kundt’s impedance tube at TSE (Tuzla, Istanbul).
Figure 6
Figure 6
In situ measurements of the classroom.
Figure 7
Figure 7
(a) Position of source and receivers; (b) Height of source and receivers.
Figure 8
Figure 8
Source and receivers’ positions in ODEON simulations. Red color symbolizes the point source and blue color represents the receivers’ position in the room.
Figure 9
Figure 9
Theoretical absorption coefficients for Prototype 1 and each of its constituting MPPs.
Figure 10
Figure 10
Absorption coefficients for Prototype 1—One layer with four parallel-arranged MPPs.
Figure 11
Figure 11
Absorption coefficients for Prototype 2—Double layer with four parallel-arranged MPPs each.
Figure 12
Figure 12
RT30 values for measured and simulated existing conditions compared to optimum ones.
Figure 13
Figure 13
RT30 values after the proposed material is used as treatment compared to optimum and existing values.
See this image and copyright information in PMC

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