A Boundary Element Method (BEM) Solver for Low Frequency Room Modes

Cicero, Andrea; Hargreaves, Jonathan A.

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 solution of 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.

Citation

Cicero, A., & Hargreaves, J. A. (2022, August). A Boundary Element Method (BEM) Solver for Low Frequency Room Modes. Presented at Internoise 2022, Glasgow, Scotland

• Presentation Conference Type: Other
• Conference Name: Internoise 2022
• Conference Location: Glasgow, Scotland
• Start Date: Aug 21, 2022
• End Date: Aug 24, 2022
• Publication Date: Aug 22, 2022
• Deposit Date: Oct 6, 2022
• Publicly Available Date: Oct 6, 2022
• DOI: https://doi.org/10.3397/in_2022_0347
• Keywords: Applied Mathematics, General Mathematics
• Publisher URL: https://internoise2022.org/
• Additional Information: Event Type : Conference