Help/UGens/Filters/AmpCompA.html

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  25 <p class="p1"><span class="s1"><b>AmpCompA</b></span><span class="s2"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></span><b>ANSI A-weighting curve</b></p>
  26 <p class="p1"><b><span class="Apple-tab-span">  </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>basic psychoacoustic amplitude compensation</b></p>
  27 <p class="p2"><br></p>
  28 <p class="p2"><br></p>
  29 <p class="p1">superclass: UGen</p>
  30 <p class="p2"><br></p>
  31 <p class="p2"><span class="Apple-tab-span">     </span></p>
  32 <p class="p1"><span class="Apple-tab-span">     </span>Higher frequencies are normally perceived as louder, which AmpCompA compensates.<span class="Apple-converted-space"> </span></p>
  33 <p class="p1"><span class="Apple-tab-span">     </span>Following the measurings by Fletcher and Munson, the ANSI standard describes<span class="Apple-converted-space"> </span></p>
  34 <p class="p1"><span class="Apple-tab-span">     </span>a function for loudness vs. frequency.<span class="Apple-converted-space"> </span></p>
  35 <p class="p1"><span class="Apple-tab-span">     </span>Note that this curve is only valid for standardized amplitude. [1]</p>
  36 <p class="p2"><span class="Apple-tab-span">     </span></p>
  37 <p class="p1"><span class="Apple-tab-span">     </span>For a simpler but more flexible curve, see <a href="AmpComp.html"><span class="s3">AmpComp</span></a></p>
  38 <p class="p2"><span class="Apple-tab-span">     </span></p>
  39 <p class="p2"><br></p>
  40 <p class="p1"><b><span class="Apple-tab-span">  </span>*ar(freq, root, minAmp, rootAmp)</b></p>
  41 <p class="p1"><b><span class="Apple-tab-span">  </span>*kr(freq, root, minAmp, rootAmp)</b></p>
  42 <p class="p1"><b><span class="Apple-tab-span">  </span>*ir(freq, root, minAmp, rootAmp)</b></p>
  43 <p class="p2"><span class="Apple-tab-span">     </span></p>
  44 <p class="p1"><span class="Apple-tab-span">     </span><b>freq</b> <span class="Apple-tab-span">        </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>input frequency value. For freq == root, the output is rootAmp. (default freq 0 Hz)</p>
  45 <p class="p1"><span class="Apple-tab-span">     </span><b>root</b><span class="Apple-tab-span"> </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>root freq relative to which the curve is calculated (usually lowest freq) (default 0 Hz)</p>
  46 <p class="p1"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>default value: C (60.midicps)</p>
  47 <p class="p2"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></p>
  48 <p class="p1"><span class="Apple-tab-span">     </span><b>minAmp</b><span class="Apple-tab-span">       </span><span class="Apple-tab-span">    </span>amplitude at the minimum point of the curve (around 2512 Hz) (default -10dB)</p>
  49 <p class="p1"><span class="Apple-tab-span">     </span><b>rootAmp</b><span class="Apple-tab-span">      </span><span class="Apple-tab-span">    </span>amplitude at the root frequency. (default 1)</p>
  50 <p class="p2"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></p>
  51 <p class="p1"><span class="s2"><span class="Apple-tab-span">    </span></span>apart from <i>freq</i>, the values are not modulatable</p>
  52 <p class="p3"><br></p>
  53 <p class="p3"><br></p>
  54 <p class="p4"><br></p>
  55 <p class="p4"><br></p>
  56 <p class="p5">// compare a sine without compensation</p>
  57 <p class="p3"><br></p>
  58 <p class="p6">{ <span class="s4">SinOsc</span>.ar(<span class="s4">MouseX</span>.kr(300, 15000, 1)) * 0.1 }.play;</p>
  59 <p class="p3"><br></p>
  60 <p class="p5">// with one that uses amplitude compensation</p>
  61 <p class="p6">(</p>
  62 <p class="p6">{<span class="Apple-converted-space"> </span></p>
  63 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">var</span> freq;</p>
  64 <p class="p6"><span class="Apple-tab-span">     </span>freq = <span class="s4">MouseX</span>.kr(300, 15000, 1);</p>
  65 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">SinOsc</span>.ar(freq) * 0.3 * <span class="s4">AmpCompA</span>.kr(freq)<span class="Apple-converted-space"> </span></p>
  66 <p class="p6">}.play;</p>
  67 <p class="p6">)</p>
  68 <p class="p3"><br></p>
  69 <p class="p3"><br></p>
  70 <p class="p5">// adjust the minimum and root amp<span class="Apple-converted-space"> </span></p>
  71 <p class="p5">// (in this way one can flatten out the curve for higher amplitudes)<span class="Apple-converted-space"> </span></p>
  72 <p class="p3"><br></p>
  73 <p class="p6">(</p>
  74 <p class="p6">{<span class="Apple-converted-space"> </span></p>
  75 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">var</span> freq;</p>
  76 <p class="p6"><span class="Apple-tab-span">     </span>freq = <span class="s4">MouseX</span>.kr(300, 18000, 1);</p>
  77 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">Formant</span>.ar(300, freq, 20, 0.1) * <span class="s4">AmpCompA</span>.kr(freq, 300, 0.6, 0.3)</p>
  78 <p class="p6">}.play;</p>
  79 <p class="p6">)</p>
  80 <p class="p3"><br></p>
  81 <p class="p5">// the curve:</p>
  82 <p class="p3"><br></p>
  83 <p class="p6">{ <span class="s4">AmpCompA</span>.ar(<span class="s4">Line</span>.ar(48, 120, 1).midicps, 48.midicps) }.plot(1.0);</p>
  84 <p class="p3"><br></p>
  85 <p class="p5">// freqs:</p>
  86 <p class="p3"><br></p>
  87 <p class="p6">{ <span class="s4">AmpCompA</span>.ar(<span class="s4">Line</span>.ar(0, 20000, 1)) }.plot(1.0);</p>
  88 <p class="p3"><br></p>
  89 <p class="p5">// compare with AmpComp (exponential decay)</p>
  90 <p class="p3"><br></p>
  91 <p class="p6">{ <span class="s4">AmpComp</span>.ar(<span class="s4">Line</span>.ar(48, 120, 1).midicps, 48.midicps) }.plot(1.0);</p>
  92 <p class="p4"><br></p>
  93 <p class="p5">// freqs:</p>
  94 <p class="p3"><br></p>
  95 <p class="p6">{ <span class="s4">AmpComp</span>.ar(<span class="s4">Line</span>.ar(40, 20000, 1), 40) }.plot(1.0);</p>
  96 <p class="p3"><br></p>
  97 <p class="p3"><br></p>
  98 <p class="p3"><br></p>
  99 <p class="p5">// amplitude compensation in frequency modulation (using Fletscher-Munson curve)</p>
 100 <p class="p6">(</p>
 101 <p class="p6">{<span class="Apple-converted-space"> </span></p>
 102 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">var</span> freq;</p>
 103 <p class="p6"><span class="Apple-tab-span">     </span>freq = <span class="s4">MouseX</span>.kr(300, 15000, 1);</p>
 104 <p class="p6"><span class="Apple-tab-span">     </span>freq = freq * <span class="s4">SinOsc</span>.ar(<span class="s4">MouseY</span>.kr(3, 200, 1), 0, 0.5, 1);</p>
 105 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">SinOsc</span>.ar(freq) * 0.1 * <span class="s4">AmpCompA</span>.ar(freq, 300)<span class="Apple-converted-space"> </span></p>
 106 <p class="p6">}.play;</p>
 107 <p class="p6">)</p>
 108 <p class="p3"><br></p>
 109 <p class="p5">// amplitude compensation in frequency modulation (using AmpComp exponential decay)</p>
 110 <p class="p6">(</p>
 111 <p class="p6">{<span class="Apple-converted-space"> </span></p>
 112 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">var</span> freq;</p>
 113 <p class="p6"><span class="Apple-tab-span">     </span>freq = <span class="s4">MouseX</span>.kr(300, 15000, 1);</p>
 114 <p class="p6"><span class="Apple-tab-span">     </span>freq = freq * <span class="s4">SinOsc</span>.ar(<span class="s4">MouseY</span>.kr(3, 200, 1), 0, 0.5, 1);</p>
 115 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">SinOsc</span>.ar(freq) * 0.1 * <span class="s4">AmpComp</span>.ar(freq, 300)<span class="Apple-converted-space"> </span></p>
 116 <p class="p6">}.play;</p>
 117 <p class="p6">)</p>
 118 <p class="p3"><br></p>
 119 <p class="p3"><br></p>
 120 <p class="p5">// without amplitude compensation</p>
 121 <p class="p6">(</p>
 122 <p class="p6">{<span class="Apple-converted-space"> </span></p>
 123 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">var</span> freq;</p>
 124 <p class="p6"><span class="Apple-tab-span">     </span>freq = <span class="s4">MouseX</span>.kr(300, 15000, 1);</p>
 125 <p class="p6"><span class="Apple-tab-span">     </span>freq = freq * <span class="s4">SinOsc</span>.ar(<span class="s4">MouseY</span>.kr(3, 200, 1), 0, 0.5, 1);</p>
 126 <p class="p6"><span class="Apple-tab-span">     </span><span class="s4">SinOsc</span>.ar(freq) * 0.1</p>
 127 <p class="p6">}.play;</p>
 128 <p class="p6">)</p>
 129 <p class="p3"><br></p>
 130 <p class="p3"><br></p>
 131 <p class="p3"><br></p>
 132 <p class="p3"><br></p>
 133 <p class="p2"><br></p>
 134 <p class="p1">[1] Function freq -&gt; dB,<span class="Apple-converted-space"> </span></p>
 135 <p class="p1"><span class="Apple-tab-span">     </span>derived from <span class="s5">http://www.beis.de/Elektronik/AudioMeasure/WeightingFilters.html</span></p>
 136 <p class="p1"><span class="Apple-tab-span">     </span>and modified to map freq -&gt; amp</p>
 137 <p class="p3"><br></p>
 138 <p class="p6">(</p>
 139 <p class="p6"><span class="s4">var</span> k =<span class="Apple-converted-space">  </span>3.5041384e16;</p>
 140 <p class="p6">var c1 = 424.31867740601;</p>
 141 <p class="p6">var c2 = 11589.093052022;</p>
 142 <p class="p6">var c3 = 544440.67046057;</p>
 143 <p class="p6">var c4 = 148698928.24309;</p>
 144 <p class="p6">f = {<span class="s4">|f|</span></p>
 145 <p class="p6"><span class="Apple-converted-space">  </span><span class="s4">var</span> r = squared(f);</p>
 146 <p class="p6"><span class="Apple-converted-space">  </span><span class="s4">var</span> m1 = pow(r,4);</p>
 147 <p class="p6"><span class="Apple-converted-space">  </span><span class="s4">var</span> n1 = squared(c1 + r);</p>
 148 <p class="p6"><span class="Apple-converted-space">  </span><span class="s4">var</span> n2 = c2 + r;</p>
 149 <p class="p6"><span class="Apple-converted-space">  </span><span class="s4">var</span> n3 = c3 + r;</p>
 150 <p class="p6"><span class="Apple-converted-space">  </span><span class="s4">var</span> n4 = squared(c4 + r);</p>
 151 <p class="p6"><span class="Apple-converted-space">  </span><span class="s4">var</span> level = k * m1 / (n1 * n2 * n3 * n4);</p>
 152 <p class="p6"><span class="Apple-converted-space">  </span>sqrt(level)</p>
 153 <p class="p6"><span class="Apple-converted-space"> </span>};</p>
 154 <p class="p6">)</p>
 155 <p class="p3"><br></p>
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