/usr/share/SuperCollider/HelpSource/Classes/AmpComp.schelp is in supercollider-common 1:3.8.0~repack-2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 | class:: AmpComp
summary:: Basic psychoacoustic amplitude compensation.
related:: Classes/AmpCompA
categories:: UGens>Analysis>Amplitude
Description::
Implements the (optimized) formula:
code::
compensationFactor = (root / freq) ** exp
::
Higher frequencies are normally perceived as louder, which AmpComp
compensates.
classmethods::
method::ar, kr, ir
argument::freq
Input frequency value. For freq == root, the output is 1.0.
argument::root
Root freq relative to which the curve is calculated
(usually lowest freq).
argument::exp
Exponent: how steep the curve decreases for increasing freq.
discussion::
Note that for frequencies very much smaller than root the amplitudes can become very high.
In this case limit the freq with code::freq.max(minval)::, or use AmpCompA.
Examples::
code::
// compare a sine without compensation
{ SinOsc.ar(MouseX.kr(300, 15000, 1)) * 0.1 }.play;
// with one that uses amplitude compensation
(
{
var freq;
freq = MouseX.kr(300, 15000, 1);
SinOsc.ar(freq) * 0.1 * AmpComp.kr(freq, 300)
}.play;
)
// different sounds cause quite different loudness perception,
// and the desired musical behavior can vary, so the exponent can be tuned:
(
{
var freq;
freq = MouseX.kr(300, 15000, 1);
Pulse.ar(freq) * 0.1 * AmpComp.kr(freq, 300, 1.3)
}.play;
)
// the curves:
// exp = 0.3333
(200,210..10000).collect {|freq| (200/freq) ** 0.3333 }.plot;
// nearly linear for semitone steps:
(48..72).midicps.collect {|freq| (48.midicps/freq) ** 0.3333 }.plot;
{ AmpComp.ar(Line.ar(48, 72, 1).midicps, 48.midicps) }.plot(1.0);
// exp = 1.2
(200,210..10000).collect {|freq| (200/freq) ** 1.2 }.plot;
(48..72).midicps.collect {|freq| (200/freq) ** 1.2 }.plot;
{ AmpComp.ar(Line.ar(48, 72, 1).midicps, 48.midicps, 1.2) }.plot(1.0);
// amplitude compensation in frequency modulation
(
{
var freq;
freq = MouseX.kr(300, 15000, 1);
freq = freq * SinOsc.ar(MouseY.kr(3, 200, 1), 0, 0.5, 1);
SinOsc.ar(freq) * 0.1 * AmpComp.ar(freq, 300)
}.play;
)
// without amplitude compensation
(
{
var freq;
freq = MouseX.kr(300, 15000, 1);
freq = freq * SinOsc.ar(MouseY.kr(3, 200, 1), 0, 0.5, 1);
SinOsc.ar(freq) * 0.1
}.play;
)
// in granular synthesis:
(
SynthDef("pgrain",
{ arg out = 0, sustain=0.01, amp=0.5, pan = 0;
var freq = MouseX.kr(300, 7000, 1);
var window = Env.sine(sustain, amp * AmpComp.ir(freq));
Out.ar(out,
Pan2.ar(
SinOsc.ar(freq),
pan
) * EnvGen.ar(window, doneAction:2)
)
}
).add;
)
// send grains
(
fork {
loop {
s.sendBundle(0.1, [\s_new, \pgrain, -1,1,1]);
0.02.wait;
};
}
)
// try different synth defs:
// without AmpComp:
(
SynthDef("pgrain",
{ arg out = 0, sustain=0.01, amp=0.5, pan = 0;
var freq = MouseX.kr(300, 7000, 1);
var window = Env.sine(sustain, amp);
Out.ar(out,
Pan2.ar(
SinOsc.ar(freq),
pan
) * EnvGen.ar(window, doneAction:2)
)
}
).add;
)
// with AmpCompA
(
SynthDef("pgrain",
{ arg out = 0, sustain=0.01, amp=0.5, pan = 0;
var freq = MouseX.kr(300, 7000, 1);
var window = Env.sine(sustain, amp * AmpCompA.ir(freq));
Out.ar(out,
Pan2.ar(
SinOsc.ar(freq),
pan
) * EnvGen.ar(window, doneAction:2)
)
}
).add;
)
::
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