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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 (−2 i 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)....
© Paul Boersma 2003-03-09