Artificial Reverberation

This chapter summarizes basic results in systems for artificial reverberation. Such systems make extensive use of tapped delay lines, comb filters, and allpass filters (described in the previous chapter).

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Subsections

• The Reverberation Problem
  • Exact Reverb via Transfer-Function Modeling
  • Complexity of Exact Reverberation
  • Possibility of a Physical Reverb Model
  
  
• Perceptual Aspects of Reverberation
  • Perception of Echo Density and Mode Density
  • Perceptual Metrics for Ideal Reverberation
    • Energy Decay Curve
    • Energy Decay Relief
  
  
• Early Reflections
• Late Reverberation Approximations
  • Desired Qualities in Late Reverberation
  • Schroeder Allpass Sections
  • Nested Allpass Filters
  
  
• A Schroeder Reverberator called JCRev
• Freeverb
  • Freeverb Main Loop
  • Moorer Lowpass Feedback Comb Filter
  • Freeverb Allpass Approximation
  • Conclusions
  
  
• FDN Reverberation
  • History of FDNs for Artificial Reverberation
  • Choice of Lossless Feedback Matrix
    • Householder Feedback Matrix
    • Most General Lossless Feedback Matrices
    • Triangular Feedback Matrices
  • Choice of Delay Lengths
    • Mean Free Path
    • Mode Density Requirement
  • Achieving Desired Reverberation Times
  • Delay-Filter Design
    • First-Order Delay-Filter Design
  • Tonal Correction Filter
  • FDNs as Digital Waveguide Networks
  • Further Extensions
    • Spatialization of Reverberant Reflections
    • Distribution of Mode Frequencies
    • Reverberation Time vs. Frequency
    • Digital Waveguide Reverberators
    • The Digital Waveguide Mesh for Reverberation
    • Time Varying Reverberators
  
  
• Problems
• More Problems

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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.