FFTSpread Spectral spread

FFTSpread.kr(chain, centroid)

Given an FFT chain, this measures the spectral spread, which is the magnitude-weighted variance. This measure can serve as an (approximate) clue towards the bandwidth of a signal (although the value is not a frequency).

The centroid should be supplied, typically using a SpecCentroid unit - if you don't fill in this argument then a SpecCentroid unit will automatically be added.

Example

// Very artificial example - just filtering some noise.

s.boot;

b = Buffer.alloc(s,2048,1);

(

x = {

var in, chain, freq, rq, val;

//freq = LFPar.kr(0.3).exprange(100, 1000);

freq = MouseY.kr(1000, 100, 1);

rq = MouseX.kr(0.001, 10, 1);

in = BPF.ar(WhiteNoise.ar, freq, rq);

chain = FFT(b.bufnum, in);

val = FFTSpread.kr(chain);

Out.ar(0, in.dup * 0.1);

(val * 0.000001).poll(10); // Poll but scaled down so more readable!

}.play(s);

)

x.free;