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## Triangular Filterbank

version 1.1.0.0 (2.59 KB) by
Frequency domain triangular filterbank with uniform spacing on arbitrarily warped frequency scale.

Updated 13 Jun 2011

Implements triangular filterbank given in . Returns matrix of M triangular filters (one per row), each K coefficients long. The triangular filters are between limits given in R (Hz) and are uniformly spaced on a warped scale defined by forward (h2w) and backward (w2h) warping functions. For example, h2w and w2h can be hz2mel and mel2hz functions, respectively, in which case trifbank returns a mel filterbank, i.e., a filterbank of triangular filters uniformly spaced on the mel scale. Other forward and backward warping functions can be specified to arrive at arbitrary warped triangular filterbanks.

 Huang, X., Acero, A., Hon, H., 2001. Spoken Language Processing: A guide to theory, algorithm, and system development. Prentice Hall, Upper Saddle River, NJ, USA (pp. 314-315).

### Cite As

Kamil Wojcicki (2021). Triangular Filterbank (https://www.mathworks.com/matlabcentral/fileexchange/31755-triangular-filterbank), MATLAB Central File Exchange. Retrieved .

suci aulia

Tom Anderson

Just a comment for Yibo Yang, if you look at the graphs above you will see that there are 50% overlaps in the mel-scale. That's standard for MFCCs.

Yibo Yang

Quick question Kamil: how can I tweak the trifbank code so that I can generate triangular filters with, say, 50% overlaps in the mel scale?

ayoub bouziane

hello, thank you for the source code ... I did not understand why you used K = nfft/2+1; and f_max = 0.5*fs; ????

Kamil Wojcicki

If all you want is a warping other than the mel scale, then the function is written to support that, i.e., no need to change trifbank.m. I would just pass different warping / unwarping functions to it:

- in MATLAB type in: help trifbank

- then try the example given there ( it will poduce a mel filterbank ), e.g.:

fs = 16000; % sampling frequency (Hz)
nfft = 2^12; % fft size (number of frequency bins)
K = nfft/2+1; % length of each filter
M = 23; % number of filters

hz2mel = @(hz)(1127*log(1+hz/700)); % Hertz to mel warping
mel2hz = @(mel)(700*exp(mel/1127)-700); % mel to Hertz warping

% Design mel filterbank of M filters each K coefficients long,
% filters are uniformly spaced on the mel scale between 0 and Fs/2
[ H1, freq ] = trifbank( M, K, [0 fs/2], fs, hz2mel, mel2hz );

hfig = figure('Position', [25 100 800 600], 'PaperPositionMode', ...
'auto', 'Visible', 'on', 'color', 'w'); hold on;

plot( freq, H1 );
xlabel( 'Frequency (Hz)' ); ylabel( 'Weight' ); set( gca, 'box', 'off');

- in the above code, the warping function are defined in following variables:

hz2mel = @(hz)(1127*log(1+hz/700)); % Hertz to mel warping
mel2hz = @(mel)(700*exp(mel/1127)-700); % mel to Hertz warping

- to use different warping functions you first have to define these, e.g., if you want uniformly spaced filters on Hz scale use:

hz2warp = @(hz)( hz );
warp2hz = @(warp)( warp );

- and make sure you then update the trifbank call with the new function handles:

[ H1, freq ] = trifbank( M, K, [0 fs/2], fs, hz2warp, warp2hz );

Alexander Sepulveda

hi,
can you help me how to implement any arbitray warping function using trifbank?. I want to implement vocal tract length normalization.

##### MATLAB Release Compatibility
Created with R2010a
Compatible with any release
##### Platform Compatibility
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