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26 <p class=
"p1"><b>SpecFlatness
<span class=
"Apple-tab-span"> </span>Spectral Flatness measure
</b></p>
27 <p class=
"p2"><br></p>
28 <p class=
"p3"><b><span class=
"Apple-tab-span"> </span>SpecFlatness.kr(chain)
</b></p>
29 <p class=
"p4"><br></p>
30 <p class=
"p3">Given an
<a href=
"FFT.html"><span class=
"s1">FFT
</span></a> chain this calculates the
<i>Spectral Flatness
</i> 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.
</p>
31 <p class=
"p4"><br></p>
32 <p class=
"p3">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.
</p>
33 <p class=
"p4"><br></p>
34 <p class=
"p4"><br></p>
35 <p class=
"p3"><b>Examples
</b></p>
36 <p class=
"p2"><br></p>
37 <p class=
"p5">s =
<span class=
"s2">Server
</span>.internal.boot;
</p>
38 <p class=
"p5">b =
<span class=
"s2">Buffer
</span>.alloc(s,
2048,
1);
</p>
39 <p class=
"p6"><br></p>
41 <p class=
"p7"><span class=
"s3">{
</span>// Example - vary mixture of white noise and pure tone with the mouse
</p>
42 <p class=
"p5"><span class=
"s2">var
</span> in, chain, flat, flatdb, flatdbsquish;
</p>
43 <p class=
"p5">in =
<span class=
"s2">XFade2
</span>.ar(
<span class=
"s2">WhiteNoise
</span>.ar,
<span class=
"s2">SinOsc
</span>.ar,
<span class=
"s2">MouseX
</span>.kr(-
1,
1));
</p>
44 <p class=
"p5">chain =
<span class=
"s2">FFT
</span>(b, in);
</p>
45 <p class=
"p5"><span class=
"s2">Out
</span>.ar(
0, in *
0.1);
</p>
46 <p class=
"p6"><br></p>
47 <p class=
"p5">flat =
<span class=
"s2">SpecFlatness
</span>.kr(chain);
</p>
48 <p class=
"p6"><br></p>
49 <p class=
"p5">flatdb =
10 * flat.log;
<span class=
"s4">// Convert to decibels
</span></p>
50 <p class=
"p5">flatdbsquish =
<span class=
"s2">LinLin
</span>.kr(flatdb, -
45, -
1.6,
0,
1).max(-
10);
<span class=
"s4">// Rescale db roughly to
0..
.1.
</span></p>
51 <p class=
"p6"><br></p>
52 <p class=
"p5">flat.poll(
10,
<span class=
"s5">"flatness: "</span>);
</p>
53 <p class=
"p5">flatdb.poll(
10,
<span class=
"s5">"flatness (db): "</span>);
</p>
54 <p class=
"p6"><br></p>
55 <p class=
"p5"><span class=
"s2">Out
</span>.kr(
0, [flat, flatdbsquish]);
</p>
56 <p class=
"p5">}.scope;
</p>
58 <p class=
"p6"><br></p>
60 <p class=
"p7"><span class=
"s3">{
</span>// Now try with your own voice
</p>
61 <p class=
"p5"><span class=
"s2">var
</span> in, chain;
</p>
62 <p class=
"p5">in =
<span class=
"s2">SoundIn
</span>.ar([
0,
1]).mean;
</p>
63 <p class=
"p5">chain =
<span class=
"s2">FFT
</span>(b, in);
</p>
64 <p class=
"p5"><span class=
"s2">Out
</span>.kr(
0, [in,
<span class=
"s2">SpecFlatness
</span>.kr(chain).poll(
1,
<span class=
"s5">"flatness: "</span>)]);
</p>
65 <p class=
"p5">}.scope;
</p>
