A Boundary Element Method (BEM) solver for low frequency room modes

Cicero, Andrea and Hargreaves, JA ORCID: https://orcid.org/0000-0003-4736-7507 2022, A Boundary Element Method (BEM) solver for low frequency room modes , in: Internoise 2022, 21-24 August 2022, Glasgow, Scotland.

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Abstract

Room modes are known to be problematic in small critical listening environments. They degrade the acoustic quality at low frequencies, producing peaks and nulls in the frequency domain and ringing in the time domain. The Finite Element Method (FEM) is currently the easiest way to predict such resonances for arbitrarily shaped rooms. This solves for mode frequencies and shapes, as well as Q-factors and decay rates. Such ‘eigenfrequency’ solvers are commonplace in FEM, but FEM has the disadvantage of needing to mesh the entire air volume in the room. The Boundary Element Method (BEM) avoids this and only requires a simple boundary mesh, but the solution to its eigenfrequency problems is much more challenging and appears in only a few academic papers. Here we transfer those approaches to Room Acoustics. We implement the block Sakurai-Sugiura method, which uses a contour integral in the complex frequency plane to convert the BEM eigenfrequency problem, which is usually non-linear in wavenumber, into a standard linear eigenfrequency problem that is straightforward to solve. The method is demonstrated through application to a cuboid room and an irregularly shaped room, both with impedance boundary conditions. Results are validated against FEM and discussed.

Item Type: Conference or Workshop Item (Paper)
Schools: Schools > School of Computing, Science and Engineering > Salford Innovation Research Centre
Journal or Publication Title: Proceedings of Internoise
Publisher: Internoise
Depositing User: Dr Jonathan Hargreaves
Date Deposited: 06 Oct 2022 12:27
Last Modified: 06 Oct 2022 12:30
URI: https://usir.salford.ac.uk/id/eprint/65060

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