Matlab for Computing Spectrograms

Octave and the Matlab Signal Processing Tool Box provide the command specgram for computing and displaying a spectrogram. As a side effect, it returns the complex STFT data in a matrix.^F.1

The spectrogram function below illustrates computation of a spectrogram in matlab for purposes of basic spectrum analysis. It is compatible with the basic functionality of Matlab's specgram function, but does not implement all of its features.

We also include invspectrogram, which provides an inversion of the spectrogram to produce the original signal (when this is possible). In other words, invspectrogram synthesizes a time-domain signal from a given STFT. Finally, testspectrogram is included for trying things out.

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Subsections

• Matlab listing: spectrogram.m
• Matlab listing: invspectrogram.m
• Matlab listing: testspectrogram.m
• Matlab listing: unwrap.m
• Non-Parametric Frequency Warping
  • Ideal Spectral Interpolation

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Order a Hardcopy of Spectral Audio Signal Processing

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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.