Spectral Flatness Measure
This function estimates the flatness of a frequency spectrum.
sfm(spec)
SFM is calculated as the ratio between the geometric mean and the
arithmetic mean :
F = N*(prod(y_i)^(1/N) / sum(y_i))
with:
y = relative amplitude of the i frequency,
and N = number of frequencies.
A single value varying between 0 and 1 is returned. The value has no unit.
The SFM of a noisy signal will tend towards 1 whereas
the SFM of a pure tone signal will tend towards 0.
See sh for another measure of signal noisiness/pureness.
Jerome Sueur sueur@mnhn.fr
a<-synth(f=8000,d=1,cf=2000,plot=FALSE) speca<-spec(a,f=8000,at=0.5,plot=FALSE) sfm(speca) # [1] 0 b<-noisew(d=1,f=8000) specb<-spec(b,f=8000,at=0.5,plot=FALSE) sfm(specb) # [1] 0.8233202
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