Virtual Instrument Design and Animation

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Virtual Instrument Design and Animation Cynthia
Bruyns Robert Taylor Carlo Séquin University of
California at Berkeley
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Aim

• To provide an environment for evaluating the
  sound qualities of modeled simple idiophones

Images courtesy of Steve Reinmuth
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Aim

• To recreate the objects sound in an interactive
  environment
• To be able to use these sounds to extend
  synthesis for computer music

Modeled Objects
Mode Activation
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Previous Sound Generation Research
Methods for sound synthesis for graphics
Stochastic Serra, X. et al. 1990 Cook, P. 2001 Textures van den Doel, K. et al. 2001 Di Fillipo, D. et al. 2000
Analytic Smith, J. 1992 Cook, P. 1995 Modal Morrison, J. et al. 1993 OBrien, J. et al. 2001
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Geometric Models

• Simple or complex shapes
• Multiple resolutions are generated
• Can use thin or solid models

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Physical Model
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Modal Formulation
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Mode Shapes (exaggerated)
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Modal Activation

• Load model geometry into viewer program.
• Choose materials parameters.
• Select several strike locations on the model
  and map to keys of a midi keyboard.
• PLAY ! Key velocity determines intensity of
  strike.

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Interactive Sound Generation

• Software created as an Audio Unit plug-in
• Can be used in AU host applications
• This allows for sound generation in a composing
  environment

Strike Location
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Sound Validation

• Synthesized sounds were compared with actual
  object sound generation
• Square plate
• Aluminum
• Steel
• Rectangular plate
• Aluminum
• Odd shaped plates
• Aluminum

Model
Real
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Measurement Setup
AnalysisWindow

• Sound dampened room
• Selection after transients
• FFT analysis of identical time intervals

Amplitude (dB)
Frequency (Hz)
?
Time (seconds)
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Square (Aluminum)
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Square (Steel)
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Rectangle (Aluminum)
604020
?
Sound Pressure Level (dB/Hz)
Materials
100 200 500 1000
2000
Model
Frequency (Hz)
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Odd Shaped Plates - S
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Odd Shaped Plates - G
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Demo Plate

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Demo Odd Shape

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Summary and Discussion

• System for generating ringing sounds
• More natural gt more interesting
• Real-time generation of strike-sounds.
• System may become predictive enough to allow
  interactive design of new bells
• Real-time shape modifications an re-analysis ?
• Extensions
• Non-linear phenomena during initial strike
• Include coupling with environment (air).

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Acknowledgements

• Apple Computer
• Ruzena Basjcy
• David Bindel
• Jon Drukman
• Justin Maxwell
• James McCartney
• Kim Silverman
• Bill Stewart