1. Interactive acoustic modeling of virtual environments Nicolas Tsingos Nicolas TsingosREVES-INRIA

2. Acoustics in virtual environments Goal: realistic sound in virtual environments Evans & Sutherland Avery Fisher Hall Id Software Driving simulator Concert hall design Video game

3. Geometrical acoustics Represent sound waves as ray paths ray paths

4. Problem: modeling diffraction Current geometric methods ignore diffraction Newton’s “Principia” (1686)

5. Problem: modeling diffraction Ignoring diffraction causes discontinuities

6. A problem: sound diffraction Ignoring diffraction causes discontinuities

7. Outline Possible approaches Possible approaches Beam tracing algorithm Beam tracing algorithm Experimental results Conclusion

8. Possible approaches Wave formulation Wave formulation Huygens-Fresnel theory Huygens-Fresnel theory Fresnel ellipsoids Fresnel ellipsoids Geometrical theory of diffraction Geometrical theory of diffraction

9. Possible approaches Wave formulation Huygens-Fresnel theory Fresnel ellipsoids Geometrical theory of diffraction Geometrical theory of diffraction Equal angles source listener

10. Geometrical Theory of Diffraction Each sequence of diffracting edges and reflecting surfaces is modeled by a single shortest path Each sequence of diffracting edges and reflecting surfaces is modeled by a single shortest path At each edge, the acoustic field is modulated by a diffraction coefficient At each edge, the acoustic field is modulated by a diffraction coefficient source listener

11. Problem to solve Efficient enumeration and construction of diffracted and reflected paths in polygonal environments

12. Outline Motivation for diffraction Possible approaches Beam tracing algorithm Beam tracing algorithm Experimental results Conclusion

13. Example beam tracing

27. Outline Motivation for diffraction Possible approaches Beam tracing algorithm Experimental results Experimental results Conclusion

28. Experimental results Evaluate sound field continuity in a complex environment source listener ~1800 polygons

29. Experimental results Position along path Power (dB) 100 50

30. Reflection only Discontinuities Position along path Power (dB) 50 100

31. Diffraction only Position along path Power (dB) 100 50 Continuous but low power

32. Reflection and diffraction Continuous reverberant sound Position along path Power (dB) 100 50

33. Applications Telepresence Telepresence Video games Video games Audio-visual production Audio-visual production Acoustic simulation of listening spaces Acoustic simulation of listening spaces

34. Video Performance Paths updated 20 times per second (R10k, 195 MHz)

35. Conclusion A beam tracing algorithm A beam tracing algorithm Efficient calculation of sound reflection and diffraction Scales well to large architectural environments Fast enough to support real-time audio rendering

36. Conclusion Diffraction … is an important acoustical effect is an important acoustical effect smoothes discontinuities smoothes discontinuities should be included in geometry-based acoustic simulation should be included in geometry-based acoustic simulation

37. Future work Signal processing Signal processing DSP hardware and software APIs Validation Validation Measurements Psychoacoustics Psychoacoustics Listening tests

38. Future work Signal processing Signal processing DSP hardware and software APIs Validation Validation Measurements Psychoacoustics Psychoacoustics Listening tests source wall panel

39. Validation in the “Bell Labs Box”

40. Want to know more ? http://www-sop.inria.fr/reves