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

Aim  To provide an environment for evaluating the sound qualities of modeled simple idiophones Images courtesy of Steve Reinmuth

Aim  To recreate the object’s sound in an interactive environment  To be able to use these sounds to extend synthesis for computer music Modeled ObjectsMode Activation

Previous Sound Generation Research Stochastic  Serra, X. et al  Cook, P Textures  van den Doel, K. et al  Di Fillipo, D. et al Analytic  Smith, J  Cook, P Modal  Morrison, J. et al  O’Brien, J. et al Methods for sound synthesis for graphics

Geometric Models  Simple or complex shapes  Multiple resolutions are generated  Can use thin or solid models

Physical Model

Modal Formulation

Mode Shapes (exaggerated)

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.

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

Sound Validation Synthesized sounds were compared with actual object sound generation  Square plate  Aluminum  Steel  Rectangular plate  Aluminum  Odd shaped plates  Aluminum ModelReal

Measurement Setup  Sound dampened room  Selection after transients  FFT analysis of identical time intervals Time (seconds) Frequency (Hz) Amplitude (dB) Analysis Window ?

Square (Aluminum) Frequency (Hz) Sound Pressure Level (dB/Hz) Materials Model

Square (Steel) Frequency (Hz) Sound Pressure Level (dB/Hz) Materials Model

Rectangle (Aluminum) Frequency (Hz) Sound Pressure Level (dB/Hz) Materials Model ?

Frequency (Hz) Sound Pressure Level (dB/Hz) Materials Model Odd Shaped Plates - “S”

Odd Shaped Plates - “G” Frequency (Hz) Sound Pressure Level (dB/Hz) Materials Model

Demo Plate

Demo Odd Shape

Summary and Discussion  System for generating “ringing” sounds  More “natural” => 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).

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