Time Varying Comb Filters

Comb filters can be changed slowly over time to produce the following digital audio ``effects'', among others:

• Phasing
• Flanging
• Chorus
• Leslie

Since all of these effects involve modulating delay length over time, and since time-varying delay lines typically require interpolation, these applications will be discussed after Chapter 3 which covers variable delay lines. For now, we will pursue what can be accomplished using fixed (time-invariant) delay lines. Perhaps the most important application is artificial reverberation, addressed in Chapter 2.

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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.