64 lines
1.5 KiB
Text
64 lines
1.5 KiB
Text
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#lang scribble/manual
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@(require (for-label racket))
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@title{SpecFlatness}
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Spectral Flatness measure@section{categories}
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UGens>FFT
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@section{related}
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Classes/SpecCentroid, Classes/SpecPcile
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@section{description}
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Given an link::Classes/FFT:: strong::chain:: this calculates the emphasis::Spectral Flatness:: measure, defined as a power spectrum's geometric mean divided by its arithmetic mean. This gives a measure which ranges from approx 0 for a pure sinusoid, to approx 1 for white noise.
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The measure is calculated linearly. For some applications you may wish to convert the value to a decibel scale - an example of such conversion is shown below.
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@section{classmethods}
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@section{method}
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kr
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@section{argument}
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buffer
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an link::Classes/FFT:: chain.
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@section{examples}
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@racketblock[
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s.boot;
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b = Buffer.alloc(s,2048,1);
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(
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{ // Example - vary mixture of white noise and pure tone with the mouse
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var in, chain, flat, flatdb, flatdbsquish;
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in = XFade2.ar(WhiteNoise.ar, SinOsc.ar, MouseX.kr(-1,1));
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chain = FFT(b, in);
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Out.ar(0, in * 0.1);
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flat = SpecFlatness.kr(chain);
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flatdb = 10 * flat.log; // Convert to decibels
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flatdbsquish = LinLin.kr(flatdb, -45, -1.6, 0, 1).max(-10); // Rescale db roughly to 0...1.
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flat.poll(10, "flatness: ");
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flatdb.poll(10, "flatness (db): ");
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Out.kr(0, [flat, flatdbsquish]);
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}.scope;
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)
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(
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{ // Now try with your own voice
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var in, chain;
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in = SoundIn.ar([0,1]).mean;
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chain = FFT(b, in);
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Out.kr(0, [in, SpecFlatness.kr(chain).poll(1, "flatness: ")]);
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}.scope;
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)
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::
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]
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