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

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