Interactive acoustic modeling of virtual environments

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Interactive acoustic modeling of virtual
environments

• Nicolas Tsingos
• REVES-INRIA

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Acoustics in virtual environments

• Goal realistic sound in virtual environments

Avery Fisher Hall
Id Software
Evans Sutherland
Driving simulator
Concert hall design
Video game
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Geometrical acoustics

• Represent sound waves as ray paths

ray paths
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Problem modeling diffraction

• Current geometric methods ignore diffraction

Newtons Principia (1686)
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Problem modeling diffraction

• Ignoring diffraction causes discontinuities

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A problem sound diffraction

• Ignoring diffraction causes discontinuities

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Outline

• Possible approaches
• Beam tracing algorithm
• Experimental results
• Conclusion

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Possible approaches

• Wave formulation
• Huygens-Fresnel theory
• Fresnel ellipsoids
• Geometrical theory of diffraction

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Possible approaches

• Wave formulation
• Huygens-Fresnel theory
• Fresnel ellipsoids
• Geometrical theory of diffraction

Equal angles
listener
source
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Geometrical Theory of Diffraction

• 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

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Problem to solve

• Efficient enumeration and construction of
  diffracted and reflected paths in polygonal
  environments

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Outline

• Motivation for diffraction
• Possible approaches
• Beam tracing algorithm
• Experimental results
• Conclusion

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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Example beam tracing
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Outline

• Motivation for diffraction
• Possible approaches
• Beam tracing algorithm
• Experimental results
• Conclusion

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Experimental results

• Evaluate sound field continuity in a complex
  environment

1800 polygons
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Experimental results
Power (dB)
100
50
Position along path
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Reflection only
Power (dB)
100
50
Position along path

• Discontinuities

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Diffraction only
Power (dB)
100
50
Position along path

• Continuous but low power

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Reflection and diffraction
Power (dB)
100
50
Position along path

• Continuous reverberant sound

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Applications

• Telepresence
• Video games
• Audio-visual production
• Acoustic simulation of listening spaces

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Video

• Performance
• Paths updated 20 times per second (R10k, 195
  MHz)

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Conclusion

• A beam tracing algorithm
• Efficient calculation of sound reflection
  anddiffraction
• Scales well to large architectural environments
• Fast enough to support real-time audio rendering

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Conclusion

• Diffraction
• is an important acoustical effect
• smoothes discontinuities
• should be included in geometry-based acoustic
  simulation

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Future work

• Signal processing
• DSP hardware and software APIs
• Validation
• Measurements
• Psychoacoustics
• Listening tests

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Future work

• Signal processing
• DSP hardware and software APIs
• Validation
• Measurements
• Psychoacoustics
• Listening tests

source
wall panel
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Validation in the Bell Labs Box
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Want to know more ?

• http//www-sop.inria.fr/reves