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WarpTB - Matlab Toolbox for Warped DSP

Aki Härmä and Matti Karjalainen

Sept. 15, 2000 - Feb 11, 2009

Note (Feb 2009)! A bug that appeared in WFIR filtering when wfilter.c (in directory /source) was compiled to mex with certain C-compilers has been corrected. New precompiled versions of wfilter.mex for recent Matlab versions are available in directory /precompiled_2009 for Windows (wfilter.mexw32, tested on XP) and Mac OSX (wfilter.mexmaci, Intel Macsonly).

Note (Jan 2008)! Users of Matlab 7.1 or later for Windows, please see this reference if/when having problems with mex-files (Thanks to Benoit Burette for pointing this out).


WarpTB is a MATLAB toolbox for frequency-warped signal processing. Practically any signal processing algorithm can be warped by replacing all the unit delay elements by first order allpass blocks. Frequency-warping changes the frequency resolution of the system. Using a suitable value for a warping coefficient LAMBDA, the frequency-resolution of the system approximates closely the frequency resolution of human auditory system. This makes frequency-warped signal processing techniques beneficial in many speech and audio signal processing applications.

If you need more information about frequency warping browse to our publications page, where you can find several papers about the topic. In particular, many of the design examples in this toolbox are related to experiments reported in [1] and [2].

WarpTB consists of a basic toolkit and a set of optional examples and sub-toolkits for specific applications. The toolbox is free and it is available at

Copyrights: Aki Härmä and Matti Karjalainen, Helsinki University of Technology, Department of Signal Processing and Acoustics (former Laboratory of Acoustics and Audio Signal Processing), Espoo, Finland.


The Matlab functions of the toolbox are available here. The (original, not updated) package can also be downloaded as a GZipped Tar file, Tar file, or zip-file.

Basically, gunzip and untar (or unzip) the package, compile the MEX files, set MATLAB's path and use. (Original) precompiled versions of MEX files for Linux and Windows are also available here. Bug-corrected new precompiled versions are available here.The functions included in the current version can be seen by saying:

>> help WarpTB

A number of demonstrations can be found from 'examples' directory.


This work has been partially supported by the Academy of Finland, the GETA graduate school, and Comsol Oy Finland.


A. Härmä, M. Karjalainen, L. Savioja, V. Välimäki, U. K. Laine, and J. Huopaniemi, ``Frequency-warped signal processing for audio applications,'' in AES 108th Convention, preprint 5171 (T-5), (Paris, France), Audio Engineering Society, February 2000.

A. Härmä, M. Karjalainen, L. Savioja, V. Välimäki, U. K. Laine, and J. Huopaniemi, ``Frequency-warped signal processing for audio applications,'' J. Aud. Eng. Soc., November 2000.

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Aki Harma