Abstract
The Boundary Element Method (BEM) is a proven numerical prediction tool for computation of room acoustic transfer functions, as are required for auralization of a virtual space. In this paper, it is validated against case studies drawn from the "Ground Truth for Room Acoustical Simulation" database within a framework that includes source and receiver directivity. These aspects are often neglected but are respectively important to include for auralisation applications because source directivity is known to affect how a room is excited and because the human auditory system is sensitive to directional cues. The framework uses weighted-sums of spherical harmonic functions to represent both the source directivity to be simulated and the pressure field predicted in the vicinity of the receiver location, the coefficients of the former being fitted to measured directivity and those of the latter computed directly from the boundary data by evaluating a boundary integral. Three validation cases are presented, one of which includes a binaural receiver. The computed results match measurements closely for the two cases conducted in anechoic conditions but show some significant differences for the third room scenario; here, it is likely that uncertainty in boundary material data limited modelling accuracy.
Highlights
This paper has proposed a framework for low-frequency room acoustic simulation, echoing similar frameworks that have been proposed for geometrical acoustics models at highfrequencies
A key component of this was the mapping proposed by Hargreaves and Lam18 to encode boundary data to spherical harmonic descriptions of the pressure field around a receiver, and verification data, results, and auralizations using that are provided
The full simulation chain was validated using three case studies drawn from the Ground truth for Room Acoustical Simulation (GRAS) database, one of which was hemi-anechoic, one fully-anechoic, and one a real room
Summary
The Boundary Element Method (BEM) is a proven numerical prediction tool for computation of room acoustic transfer functions, as are required for auralization of a virtual space In this paper, it is validated against case studies drawn from the “Ground Truth for Room Acoustical Simulation” database within a framework that includes source and receiver directivity. This approach is widely accepted by the sound-field rendering community as an appropriate encoding format for both loudspeaker array-based and binaural reproduction systems, and has the added benefit from a prediction-algorithm verification perspective of separating validation of the prediction and rendering processes It is consistent with an equivalent representation at high frequencies and, noting that a similar approach may be used to encode source directivity, leads to point-to-point room transfer functions being thought of as having multiple input and output channels.. It is consistent with an equivalent representation at high frequencies and, noting that a similar approach may be used to encode source directivity, leads to point-to-point room transfer functions being thought of as having multiple input and output channels. Encoding to such a format from BEM, FEM, or FDTD has to date been achieved by simulating some type of microphone array. Encoding of this data is, not straightforward and is constrained by many of the factors that affect real microphone array design, with tradeoffs having to be made between array size and density and encoding accuracy
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