Specific Time-Varying Delay Effects

Time varying delay lines are fundamental building blocks for delay effects, synthesis algorithms, and computational acoustic models of musical instruments.

In the category of delay effects, variable delay lines are used for

• Phasing
• Flanging
• Chorus
• Leslie
• Reverb

(While reverberators need not be time varying, nowadays they typically are [102,58].)

In digital waveguide synthesis, variable delay lines are used for

• Vibrating strings (guitars, violins, ...)
• Woodwind bores
• Horns
• Tonal percussion (rods, membranes)

The following sections will elaborate on the use of variable delay lines for effects. Their use in digital waveguide models will be deferred to a later chapter.

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Subsections

• Flanging
  • Flanger Speed and Excursion
  • Flanger Depth Control
  • Flanger Inverted Mode
  • Flanger Feedback Control
  • Summary of Flanging
  
  
• Phasing
• Vibrato Simulation
• Doppler Effect
  • Vector Formulation
  
  
• Doppler Simulation
  • Doppler Simulation via Delay Lines
  • Time-Varying Delay-Line Reads
  • Multiple Read Pointers
  • Multiple Write Pointers
  • Stereo Processing
  • System Block Diagram
  
  
• Chorus Effect
• The Leslie
  • Rotating Horn Simulation
  • Leslie Free-Field Horn Measurements
  • Separating Horn Output from Base Leakage
  
  
• Rotating Woofer-Port and Cabinet Simulation
• Miscellaneous Effects
  • Doubling Simulation
  • Slap Back

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Previous: Large Delay Changes
Next: Flanging

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written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.