(Extremely) Simplified Model of Speech

Production

Periodicsource

Noisesource

Filtersvoiced

unvoiced Coupling Speech

Channel Vocoder, Synthesizer component

Channel Vocoder, Analyzer component

Vocoders: vocal tract synthesis

•Short time spectral synthesis

•Linear predictive synthesis

•Cepstral synthesis

•Formant synthesis

Vocoders: vocal tract analysis

•Short time spectral analysis

•Linear predictive analysis

•Cepstral analysis

•Formant analysis

Vocoders: vocal source analysis

•Pitch detection

•Voiced/unvoiced decision

Fine structure and Spectral Envelope

Narrow and wideband filterbank spectral analyses

Wideband spectrogram

Figure 3.5: Narrow band spectrogramNarrowband spectrogram

•Source-Filter Separation by Cepstral Analysis

LPC spectral envelope estimation

Formant Analysis•Peak picking from smoothed spectrum

• Root-finding from LPC polynomial - finding second-order sections

•In general, position more important than bandwidth

•Deterministic or statistical analysis to find best formant “track”

http://ptolemy.eecs.berkeley.edu/~eal/audio/vocoder.html

Ed Lee Vocoder Page

http://www.sirlab.de/linux/descr_vocoder.html

Linux Vocoder Page

How does the speech sound with the middle spectrum differ from the left one?

From the right?