yvan volochine wrote:
> Could someone explain me how I can make a notch with biquad~ (or with
> any other native pd objects) please ?
A notch filter is basically this in a z-plane plot:
|
| o cos(a), sin(a)
| x r*cos(a), r*sin(a)
|
--------+--------
|
| x r*cos(a), -r*sin(a)
| o cos(a), sin(a)
|
Where:
o = zero on unit circle
x = pole just inside unit circle
Parameters:
a = 2*pi*frequency/samplerate (zero+pole angle)
r = just less than 1 (pole radius)
The closer r is to 1, the narrower the notch is.
Pd objects:
samplerate~
czero~
cpole~
expr~ -- for accuracy
cos~ -- for speed, note cos~ expects 0..1 instead of 0..2PI
See also:
http://crca.ucsd.edu/~msp/techniques/latest/book-html/node144.html
Hope this helps,
Claude
--
http://claudiusmaximus.goto10.org
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