A Trial Acoustic Improvement in a Lecture Hall with MPP Sound Absorbers and FDTD Acoustic Simulations

Abstract

Sound absorbing micro-perforated panels (MPPs) are being increasingly used because of their high quality in terms of hygiene, sustainability and durability. The present work investigates the feasibility and the performance of MPPs when used as an acoustic treatment in lecture rooms. With this purpose, three different micro-perforated steel specimens were first designed following existing predictive models and then physically manufactured through 3D additive metal printing. The specimens’ acoustic behavior was analyzed with experimental measurements in single-layer and double-layer configurations. Then, the investigation was focused on the application of double-layer MPPs to the ceiling of an existing university lecture hall to enhance speech intelligibility. Numerical simulations were carried out using a full-spectrum wave-based method: a finite-difference time-domain (FDTD) code was chosen to better handle time-dependent signals as the verbal communication. The present work proposes a workflow to explore the suitability of a specific material to speech requirements. The measured specific impedance complex values allowed to derive the input data referred to MPPs in FDTD simulations. The outcomes of the process show the influence of the acoustic treatment in terms of reverberation time (T30) and sound clarity (C50). A systematic comparison with a standard geometrical acoustic (GA) technique is reported as well.

High potential of small-room acoustic modeling with 3D time-domain finite element method

“…A wide variety of numerical methods are available for timedomain simulations: finite-difference time-domain (FDTD) (Sakamoto, 2007;Kowalczyk and van Walstijn, 2008;Sakamoto et al, 2008;Kowalczyk and van Walstijn, 2011;Hamilton and Bilbao, 2017;Toyoda and Eto, 2019;Cingolani et al, 2021;Toyoda and Sakayoshi, 2021) or finite-volume timedomain (FVTD) methods (Bilbao, 2013;Bilbao et al, 2016), time-domain BEM (TD-BEM) (Hargreaves and Cox, 2008), time-domain FEM (TD-FEM) (Okuzono et al, 2019;Yoshida et al, 2022), time-domain discontinuous Galerkin FEM (DG-FEM) (Simonaho et al, 2012;Wang et al, 2019;Wang and Hornikx, 2020;Pind et al, 2021), time-domain spectral element method (TD-SEM) (Pind et al, 2019), pseudospectral timedomain (PSTD) method (Hornikx et al, 2015;Hornikx et al, 2016), and adaptive rectangular decomposition (ARD) method (Mehra et al, 2012;Morales et al, 2015;Rabisse et al, 2019). They respectively offer several benefits in terms of ease of coding and applicability of complex geometries and so on according to fundamental algorithms of numerical methods.…”

Special Issue: Advances in Architectural Acoustics

“…The feasibility and performance of micro-perforated panels (MPPs) when used as an acoustic treatment in lecture rooms were investigated in this work by Cingolani et al [13]. Three different micro-perforated steel specimens were first designed following existing predictive models and then physically manufactured through 3D additive metal printing.…”

Improving Insertion Loss of Sonic Crystal Active Noise Barrier by Reinforcement Learning and Finite Difference Time Domain Simulations

“…A parallel approach suitable for acoustic purposes has emerged with success in different applications. These applications encompass but are not limited to sound diffusers [22], [23], absorbing panels [44] and sonic crystal waveguides [45] and SCNB [46].…”