Simulations of room acoustics using fast multipole boundary element methods

Room impulse responses can be simulated using various methods that differ in their computational complexity and accuracy. While boundary element methods (BEM) potentially can provide accurate simulations in complex geometries including effects such as diffraction and absorption, their use is limited due to relatively large values of parameter kD (k is the wavenumber and D is the room diameter). The size of the mesh also grows as the square of this parameter. We show that the fast multipole (FMM) accelerated BEM realized on multicore workstations can handle problems for rooms of D ∼ 10 m for the frequency range up to ~5 kHz (kD ∼ 1000). For such problems, needing meshes with several million elements, stable and efficient methods for high frequency FMM are needed. We discuss these issues and demonstrate results of such computations both in frequency and time domains. In simple cases numerical solutions are compared with analytical solutions obtained by the method of images. For more complex cases including rooms of different shapes with baffles and openings two methods, the direct and indirect BEM, are studied and their performance discussed. [This work is supported by VisiSonics Corporation.]