“Modeling acoustics in virtual environments using the uniform theory of diffraction” by Tsingos, Funkhouser, Ngan and Carlbom

Realistic modeling of reverberant sound in 3D virtual worlds provides users with important cues for localizing sound sources and understanding spatial properties of the environment. Unfortunately, current geometric acoustic modeling systems do not accurately simulate reverberant sound. Instead, they model only direct transmission and specular reflection, while diffraction is either ignored or modeled through statistical approximation. However, diffraction is important for correct interpretation of acoustic environments, especially when the direct path between sound source and receiver is occluded.
The Uniform Theory of Diffraction (UTD) extends geometrical acoustics with diffraction phenomena: illuminated edges become secondary sources of diffracted rays that in turn may propagate through the environment. In this paper, we propose an efficient way for computing the acoustical effect of diffraction paths using the UTD for deriving secondary diffracted rays and associated diffraction coefficients. Our main contributions are: 1) a beam tracing method for enumerating sequences of diffracting edges efficiently and without aliasing in densely occluded polyhedral environments; 2) a practical approximation to the simulated sound field in which diffraction is considered only in shadow regions; and 3) a real-time auralization system demonstrating that diffraction dramatically improves the quality of spatialized sound in virtual environments.

1. J.M. Airey, J.H. Rohlf, and F.P. Brooks, Jr. Towards image realism with interactive update rates in complex virtual building environments. In Rich Riesenfeld and Carlo Sequin, editors, Computer Graphics (1990 Symposium on Interactive 3D Graphics), pages 41-50, March 1990.
2. L. Aveneau and M. Meriaux. Rendering polygonal scenes with diffraction account. Seventh International Conference in Central Europe on Computer Graphics and Visualization (Winter School on Computer Graphics), February 1999.
3. L. Aveneau, Y. Pousset, R. Vauzelle, and M. Meriaux. Development and evaluations of physical and computer optimizations for the 3d utd model. AP2000 Millennium Conference on Antennas & Propagation (poster), April 2000.
4. H.L. Bertoni. Coverage prediction for mobile radio systems operating in the 800/900 MHz frequency range. IEEE Transactions on Vehicular Technology (Special Issue on Mobile Radio Propagation), 37(1), February 1988.
5. J. Blauert. Spatial Hearing : The Psychophysics of Human Sound Localization. M.I.T. Press, Cambridge, MA, 1983.
6. M. Born and E. Wolf. Principles of Optics. 7th ed., Pergamon Press, 1999.
7. B.-I. L. Dalenback. Room acoustic prediction based on a unified treatment of diffuse and specular reflection. J. of the Acoustical Soc. of America, 100:899- 909, 1996.
8. G. Drettakis. Structured Sampling and Reconstruction of Illumination for Image Synthesis. PhD thesis, University of Toronto, January 1994.
9. N.I. Durlach and A.S. Mavor. Virtual reality scientific and technological challenges. National Research Council Report, National Academy Press, 1995.
10. P. Filippi, D. Habault, J.P. Lefevre, and A. Bergassoli. Acoustics, basic physics, theory and methods. Academic Press, 1999.
11. S.J. Fortune. Topological beam tracing. In Proc. 15th ACM Symposium on Computational Geometry, pages 59-68, 1999.
12. T. Funkhouser, I. Carlbom, G. Elko, G. Pingali, M. Sondhi, and J. West. A beam tracing approach to acoustic modeling for interactive virtual environments. ACM Computer Graphics, Proc. SIGGRAPH98, pages 21-32, July 1998.
13. T. Funkhouser, P. Min, and I. Carlbom. Real-time acoustic modeling for distributed virtual environments. ACM Computer Graphics, Proc. SIGGRAPH99, pages 365-374, August 1999.
14. J. Goodman and J. O’Rourke, editors. Handbookof Discrete and Computational Geometry. CRC Press, 1997.
15. P. Heckbert and P. Hanrahan. Beam tracing polygonal objects. Computer Graphics (SIGGRAPH84), 18(3):119-127, July 1984.
16. D.C. Hothersall, S.N. Chandler-Wilde, and M.N. Hajmirzae. Efficiency of single noise barriers. J. of Sound and Vibration, 146(2):303-322, 1991.
17. C. Huygens. Traite de la Lumiere. London, Macmillan & Co., 1912.
18. P. Jean. A variational approach for the study of outdoor sound propagation and application to railway noise. J. of Sound and Vibration, 212(2):275-294, 1998.
19. C. B. Jones. A new approach to the `hidden line’ problem. Computer Journal, 14(3):232-237, August 1971.
20. T. Kawai. Sound diffraction by a many sided barrier or pillar. J. of Sound and Vibration, 79(2):229-242, 1981.
21. J.B. Keller. Geometrical theory of diffraction. J. of the Optical Society of America, 52(2):116-130, 1962.
22. S.C. Kim, B. Guarino, T. Willis, V. Erceg, S. Fortune, R. Valenzuela, L. Thomas, J. Ling, and J. Moore. Radio propagation measurements and prediction using three-dimensional ray tracing in urban environments at 908 MHz and 1.9 GHz. IEEE Trans. on Vehicular Technology, 48:931-946, 1999.
23. M. Kleiner, B.I. Dalenbak, and P. Svensson. Auralization – an overview. J. of the Audio Engineering Society, 41(11):861-875, November 1993.
24. R.G. Kouyoumjianand P.H. Pathak. A uniform geometrical theory of diffraction for an edge in a perfectly conducting surface. Proc. of IEEE, 62:1448-1461, November 1974.
25. H. Lehnert and J. Blauert. Principles of binaural room simulation. Applied Acoustics, 36:259-291, 1992.
26. D.A. McNamara, C.W.I. Pistorius, and J.A.G. Malherbe. Introduction to the Uniform Geometrical Theory of Diffraction. Artech House, 1990.
27. H. Medwin, E. Childs, and G. Jebsen. Impulse studies of double diffraction: A discrete huygens interpretation. J. Acoust. Soc. Am., 72:1005-1013, 1982.
28. P. Min and T. Funkhouser. Priority-driven acoustic modeling for virtual environments. Proc. Eurographics’2000, 2000.
29. J. S. B. Mitchell. Geometric shortest paths and network optimization. In Jorg-R udiger Sack and Jorge Urrutia, editors, Handbookof Computational Geometry. Elsevier Science Publishers B.V. North-Holland, Amsterdam, 1998.
30. B. C.J. Moore. An introduction to the psychology of hearing. Academic Press, 4th ed., 1997.
31. A.D. Pierce. Acoustics. An introduction to its physical principles and applications. 3rd ed., American Institute of Physics, 1984.
32. W. Press, S. Teukolsky, W. Vetterling, and B. Flannery. Numerical Recipes in C, 2nd ed. Cambridge University Press, New York, 1992.
33. A. Rajkumar, B.F. Naylor, F. Feisullin, and L. Rogers. Predicting RF coverage in large environments using ray-beam tracing and partitioning tree represented geometry. Wireless Networks, 2(2):143-154, 1996.
34. L. Savioja, J. Huopaniemi, T. Lokki, and R. Vaananen. Creating interactive virtual acoustic environments. J. of the Audio Engineering Society, 47(9):675- 705, September 1999.
35. J. Stam. Diffraction shaders. ACM Computer Graphics, Proc. SIGGRAPH99, pages 101-110, August 1999.
36. U. Stephenson and U. Kristiansen. Pyramidal beam tracing and time dependent radiosity. 15th International Congress on Acoustics, pages 657-660, June 1995.
37. R. L. Storms. Auditory-Visual Cross-Modal Perception Phenomena. PhD thesis, Naval Postgraduate School, Monterey, California, September 1998.
38. U. P. Svensson, R. I. Fred and J. Vanderkooy Analytic secondary source model of edge diffraction impulse responses. J. of the Acoustical Society of America, 106:2331-2344, 1999.
39. S. Teller. Computing the antiumbra cast by an area light source. Computer Graphics (SIGGRAPH92), 26(2):139-148, 1992.
40. S. Teller. Visibility Computations in Densely Occuded Polyhedral Environments. PhD thesis, Computer Science Div., Univ. of California, Berkeley, 1992.
41. R. Torres, P. Svensson and M. Kleiner. Computation of edge diffraction for more accurate room acoustics auralization. J. of the Acoustical Society of America, 109:600-610, 2001.
42. R. Torres. Studies of Edge Diffraction and Scattering: Applications to Room acoustics and Auralization. PhD thesis, Dept. of Applied Acoustics, Chalmers University of Technology, Sweden, 2000.
43. N. Tsingos and J.-D. Gascuel. Soundtracks for computer animation: sound rendering in dynamic environments with occlusions. Proceedings of Graphics In-terface’97, pages 9-16, May 1997.