A command to filter every selected Sound object, with a single formant of a specified frequency and bandwidth.
Two recursive filter coefficients are computed as follows:
|p = –2 exp (–π bandwidth dt) cos (2π frequency dt)|
|q = exp (–2π bandwidth dt)|
where dt is the sample period. The new signal y is then computed from the old signal x and itself as
|y1 := x1|
|y2 := x2 – p y1|
|∀n ≥ 3: yn := xn – p yn-1 – q yn-2|
After filtering, the sound y is scaled so that its absolute extremum is 0.9.
For a comparative discussion of various filtering methods, see the Filtering tutorial.
This filter has an in-place version: Sound: Filter with one formant (in-place)....
© ppgb, March 9, 2003