[PD] fft newbie - rifft~ filter

PSPunch shima at pspunch.com
Tue Jul 1 00:37:26 CEST 2008

> hi all,
> today I start learning FFT, and after seeing the (hann) windowing 
> function, I realized this (attached) filter with custom frequency 
> response, but I suspect something is wrong here
> why it sucks (given that it does)?
> also I get a fixed frequency around 60Hz, why?

[phasor~] takes a range of 0 to 1.
To fully drive your speakers, you may want to insert a [-~ 0.5] after 
[phasor~] so that you get a range of -0.5 to 0.5, centered at zero.
You can then multiply the amplitude by 2 (instead of 1 which you 
currently have your slider range set to)

This should also removed the 60Hz tone you were hearing.

Actually, the tone you were hearing was probably 86Hz if you are 
processing audio at a sample rate of 44,100Hz.

By multiplying the source with a hanning window, you are actually 
applying a kind of an amplitude modulation. Artifacts caused by this 
procedure may become a little more apparent when you use live sounds for 

David Shimamoto

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