Vocoders

The term ``vocoder'' derives from ``voice coder'', and it is the name for a class of analysis/synthesis methods based on filter-bank analysis. In fact, it is one of the oldest ``sub-band coding'' schemes, dating back to the 1930s at Bell Telephone Laboratories [223,60]. The purpose of this chapter is to briefly describe various vocoders in chronological order, primarily for historical perspective. Today, the term ``vocoder'' has become somewhat synonymous with ``modified short-time Fourier transform,'' and vocoders, as historically defined, appear to be rarely used.

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Subsections

• Dudley's Channel Vocoder
• Vocoder Summary
• Vocoder Analysis
• Computing the Vocoder Parameters
• Phase Vocoder Implementation via FFT
• Further Reading on the Vocoder

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Order a Hardcopy of Spectral Audio Signal Processing

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Next: Dudley's Channel Vocoder

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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.