Elementary Audio Digital Filters

This appendix is devoted to small but useful digital filters that are commonly used in audio applications. Analytical tools from the main chapters are used to analyze these ``audio gems''.

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Subsections

• Elementary Filter Sections
  • One-Zero
  • One-Pole
  • Two-Pole
    • Resonator Bandwidth in Terms of Pole Radius
  • Two-Zero
  • Complex Resonator
    • Two-Pole Partial Fraction Expansion
  • The BiQuad Section
  • Biquad Software Implementations
  
  
• Allpass Filter Sections
  • The Biquad Allpass Section
  • Allpass Filter Design
  
  
• DC Blocker
  • DC Blocker Frequency Response
  • DC Blocker Software Implementations
  
  
• Low and High Shelving Filters
  • Exercise
  
  
• Peaking Equalizers
• Time-Varying Two-Pole Filters
  • Normalizing Two-Pole Filter Gain at Resonance
  • Constant Resonance Gain
  • Peak Gain Versus Resonance Gain
  • Constant Peak-Gain Resonator
  • Four-Pole Tunable Lowpass/Bandpass Filters
  
  
• Elementary Filter Problems

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Order a Hardcopy of Introduction to Digital Filters

Previous: Phasor Analysis: Factoring a Complex Sinusoid into Phasor Times Carrier
Next: Elementary Filter Sections

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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.