# Why my mel filters do not overlap on each other?

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cat0530 on 18 Mar 2016
Edited: cat0530 on 21 Mar 2016
The 26 filters should overlap on each other. Could someone help me with this?
Star Strider on 18 Mar 2016
I’ve never used or designed MEL filters. I refer you to: Mel Frequency Cepstral Coefficient (MFCC) tutorial since it seems to be a comprehensive discussion. Compare your code with that discussion.

Rick Rosson on 20 Mar 2016
Edited: Rick Rosson on 21 Mar 2016
I think the problem is in the second elseif statement:
elseif (k>=f_range(m+1) && k<=f_range(m))
These two sub-conditions are mutually exclusive, so this condition is always false. As a result, the line after this condition, which creates the right half of the triangle, is never executed.
elseif (k>f_range(m) && k<=f_range(m+1))
That being said, there are much easier and more efficient ways to create the filter bank in MATLAB, for example:
• logical indexing
• the tripuls function
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cat0530 on 21 Mar 2016
Yes, you're right. I've changed the second statement and it works! Now the problem is that only 24 filters are shown in the graph instead of 26. I've tried changing the outer for loop but it says index out of bounds
Rick Rosson on 21 Mar 2016
You need to create 2 extra points in f_range. So replace the following two lines:
%Need 26 points spaced linearly between minfreq and maxfreq
f_range = linspace(minMel, maxMel, nfilts);
with these two:
%Need 28 points spaced linearly between minfreq and maxfreq
f_range = linspace(minMel, maxMel, nfilts+2);

### More Answers (1)

Rick Rosson on 20 Mar 2016
Edited: Rick Rosson on 20 Mar 2016
Please review the tripuls function.
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Star Strider on 20 Mar 2016
I’m not certain that will work. When I looked up the MEL filters (that are designed to emulate cochlear frequency responses), the pass-bands were intersecting and looked something like: ...XXXXX...
Rick Rosson on 20 Mar 2016
It will work. I've used it successfully.