Sound: To MelSpectrogram...
A command that creates a MelSpectrogram object from every selected Sound object by band filtering in the frequency domain with a set of triangular filters.
The filter functions used are all triangular in shape on a mel frequency scale. Each filter function depends on three parameters, the lower frequency fl, the central frequency fc and the higher frequency fh. On a mel scale, the distances fc-fl and fh-fc are equal for each filter. The filter function is as follows:
H(f) = 0 for f ≤ fl and f ≥ fh|
H(f) = (f - fl) / (fc - fl) for fl ≤ f ≤ fc|
H(f) = (fh - f) / (fh - fc) for fc ≤ f ≤ fh|
In general the number of filter values stored in each frame of the MelSpectrogram is an order of magnitude smaller than the number of sound samples in the corresponding analysis frame.
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© djmw, October 22, 2014