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Interactive acoustic modeling
of virtual environments
Interactive acoustic modeling
of virtual environments
Nicolas Tsingos Nicolas Tsingos
REVES-INRIAREVES-INRIA
Acoustics in virtual environmentsAcoustics in virtual environments
Goal: realistic sound in virtual Goal: realistic sound in virtual environments environments
Evans & Sutherland Avery Fisher HallId Software
Drivingsimulator
Concert hall design
Videogame
Geometrical acousticsGeometrical acoustics
Represent sound waves as ray pathsRepresent sound waves as ray paths
ray paths
Problem: modeling diffractionProblem: modeling diffraction
Current geometric methods ignore Current geometric methods ignore diffractiondiffraction
Newton’s “Principia” (1686)
Problem: modeling diffractionProblem: modeling diffraction
Ignoring diffraction causes discontinuitiesIgnoring diffraction causes discontinuities
A problem: sound diffractionA problem: sound diffractionIgnoring diffraction causes discontinuitiesIgnoring diffraction causes discontinuities
OutlineOutline
• Possible approachesPossible approaches
• Beam tracing algorithmBeam tracing algorithm
•Experimental results
•Conclusion
Possible approachesPossible approaches
• Wave formulationWave formulation
• Huygens-Fresnel theoryHuygens-Fresnel theory
• Fresnel ellipsoidsFresnel ellipsoids
• Geometrical theory of diffractionGeometrical theory of diffraction
Possible approachesPossible approaches
•Wave formulation
•Huygens-Fresnel theory
•Fresnel ellipsoids
• Geometrical theory of diffractionGeometrical theory of diffraction
Equal anglesEqual angles
source
listener
Geometrical Theory of DiffractionGeometrical Theory of Diffraction• Each sequence of diffracting edges Each sequence of diffracting edges
and reflecting surfaces is modeled by and reflecting surfaces is modeled by a single shortest patha single shortest path
• At each edge, the acoustic field is At each edge, the acoustic field is modulated by a diffraction coefficient modulated by a diffraction coefficient
source
listener
Problem to solveProblem to solve
Efficient enumeration and Efficient enumeration and construction of diffracted and construction of diffracted and reflected paths in polygonal reflected paths in polygonal environmentsenvironments
OutlineOutline
•Motivation for diffraction
•Possible approaches
• Beam tracing algorithmBeam tracing algorithm
•Experimental results
•Conclusion
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
Example beam tracingExample beam tracing
OutlineOutline
•Motivation for diffraction
•Possible approaches
•Beam tracing algorithm
• Experimental resultsExperimental results
•Conclusion
Experimental resultsExperimental results
Evaluate sound field continuity in a Evaluate sound field continuity in a complex environmentcomplex environment
source
listener
~1800 polygons
Experimental resultsExperimental results
Position along path
Power (dB)
100
50
Reflection onlyReflection only
Discontinuities
Position along path
Power (dB)
50
100
Diffraction onlyDiffraction only
Position along path
Power (dB)
100
50
Continuous but low power
Reflection and diffractionReflection and diffraction
Continuous reverberant soundPosition along path
Power (dB)
100
50
ApplicationsApplications
• TelepresenceTelepresence
• Video gamesVideo games
• Audio-visual productionAudio-visual production
• Acoustic simulation of listening Acoustic simulation of listening spacesspaces
VideoVideo
PerformancePerformance•Paths updated 20 times per second
(R10k, 195 MHz)
ConclusionConclusion
• A beam tracing algorithmA beam tracing algorithm•Efficient calculation of sound reflection and
diffraction
•Scales well to large architectural environments
•Fast enough to support real-time audio rendering
ConclusionConclusion
Diffraction …Diffraction …
• is an important acoustical effectis an important acoustical effect
• smoothes discontinuitiessmoothes discontinuities
• should be included in geometry-should be included in geometry-based acoustic simulationbased acoustic simulation
Future workFuture work
• Signal processingSignal processing• DSP hardware and software APIs
• ValidationValidation• Measurements
• PsychoacousticsPsychoacoustics•Listening tests
Future workFuture work
• Signal processingSignal processing• DSP hardware and software APIs
• ValidationValidation• Measurements
• PsychoacousticsPsychoacoustics•Listening tests
source
wall panel
Validation in the “Bell Labs Box”Validation in the “Bell Labs Box”
Want to know more ?Want to know more ?
http://www-sop.inria.fr/reveshttp://www-sop.inria.fr/reves
