Fast Time-Domain Edge-Diffraction Calculations for Interactive Acoustic Simulations
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Research Article Fast Time-Domain Edge-Diffraction Calculations for Interactive Acoustic Simulations Paul T. Calamia1, 2 and U. Peter Svensson3 1 Program
in Architectural Acoustics, School of Architecture, Rensselaer Polytechnic Institute, Troy, NY 12180, USA of Computer Science, Princeton University, Princeton, NJ 08544, USA 3 Acoustics Research Centre, Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway 2 Department
Received 1 May 2006; Revised 20 September 2006; Accepted 16 October 2006 Recommended by Werner De Bruijn The inclusion of edge diffraction has long been recognized as an improvement to geometrical-acoustics (GA) modeling techniques, particularly for acoustic simulations of complex environments that are represented as collections of finite-sized planar surfaces. One particular benefit of combining edge diffraction with GA components is that the resulting total sound field is continuous when an acoustic source or receiver crosses a specular-zone or shadow-zone boundary, despite the discontinuity experienced by the associated GA component. In interactive acoustic simulations which include only GA components, such discontinuities may be heard as clicks or other undesirable audible artifacts, and thus diffraction calculations are important for high perceptual quality as well as physical realism. While exact diffraction calculations are difficult to compute at interactive rates, approximate calculations are possible and sufficient for situations in which the ultimate goal is a perceptually plausible simulation rather than a numerically exact one. In this paper, we describe an edge-subdivision strategy that allows for fast time-domain edge-diffraction calculations with relatively low error when compared with results from a more numerically accurate solution. The tradeoff between computation time and accuracy can be controlled with a number of parameters, allowing the user to choose the speed that is necessary and the error that is tolerable for a specific modeling scenario. Copyright © 2007 P. T. Calamia and U. P. Svensson. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1.
INTRODUCTION
Edge-diffraction impulse responses (IRs) are useful for acoustic simulations involving objects or environments comprising faceted surfaces and have been applied to many problems in acoustics such as loudspeaker radiation [1], noise-barrier analysis [2], and room-acoustics modeling [3]. Diffraction calculations correct for the high-frequency approximation inherent in modeling techniques based on geometrical-acoustics (GA) assumptions, allow for the modeling of sound propagation around occluders and into shadow zones, and provide a smooth, continuous soundfield at specular-zone and shadow-zone boundaries when combined with GA components. All of these factors are important to achieve perceptual realis
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