noverlap argument to spectrogram

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Steven
Steven on 16 Aug 2011
The documentation for noverlap says that it indicates the "number of overlap samples." But this seems unclear. Suppose I have an noverlap of 1. Does that mean that a given window will overlap exactly one sample with the following window and 0 with the preceding, or that it will overlap one sample with the preceding and succeeding windows? If it is the former, that seems odd, because it would mean that for odd noverlap, different windows would look different with regards to overlap (you would have pairs of windows that overlap, but no pair overlaps with another. This also creates an ambiguity if you have an odd number of windows), but if it's the latter then the documentation is technically incorrect, so which is it?

Accepted Answer

Daniel Shub
Daniel Shub on 17 Aug 2011
While I haven't tested it, and I cannot think of an easy signal that would allow me to, I believe that noverlap refers to the amount of overlap of window N with window N-1.
  1 Comment
Steven
Steven on 19 Aug 2011
I came up with some tests, and determined that you are right:
>> S=spectrogram([1:10000], 20, 0); size(S)
ans =
129 500
>> S=spectrogram([1:10000], 20, 5); size(S)
ans =
129 666
>> S=spectrogram([1:10000], 20, 10); size(S)
ans =
129 999

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