[chuck-users] filter

eduard aylon eduard.aylon at gmail.com
Sat Jul 1 08:00:33 EDT 2006

On Jul 1, 2006, at 11:38 AM, Atte André Jensen wrote:

> Adam Tindale wrote:
>> There are a few examples of filtering that come with ChucK. The best
>> ones are wind.ck and wind2.ck, as well as powerup.ck.
> I did have a look, and found that something like this gives a decent
> resonant low-pass filter:
> triosc tri => ADSR env => TwoPole filter => dac;
> sqrosc sqr => env;
> 1 => filter.norm;
> 1500 => filter.freq;
> .97=> filter.radius;
> Seems that the radius is "filter strength", setting it to 0 and the
> filter just passes the signal through. However I still need to be able
> to get rid of the resonance. And a high-pass version would be nice  
> too.
> Could someone explain that the coefficients mean? (or link to some
> material that explains it)...

Try having a look at http://ccrma.stanford.edu/~jos/filters/ 
As a quick summary, think of poles as if they were peaks, and zeros  
as valleys. This way you will attenuate frequencies where you put  
zeros, and enhance them if you place poles.

If you (or anyone who's willing to try) were on Mac OS X you can try  
playing with a filter design software I am working on, http://student- 
kmt.hku.nl/~eduard/qPOZE/qPoze_a01_pkg.tgz. It is still on an  
experimental phase and haven't (extensively) test it on other  
machines than mine, yet.... so if you try it out, please let me know  
of any issues you may encounter. If installation succeeds, you can  
place any number of poles/zeros in the z-plane (unit circle) and move  
them arround with the mouse. This way you may understand how poles  
and zeros affect the amplitude/phase response.

hope this helps,


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