Sound: Filter (one formant)...

A command to filter every selected Sound object, with a single formant of a specified frequency and bandwidth.

Algorithm

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 := x2p y1
n ≥ 3: yn := xnp yn-1q 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-line version: Sound: Filter with one formant (in-line)....


© ppgb, March 9, 2003