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<h2>
<span class="refentrytitle">areson</span>
</h2>
<p>areson —
A notch filter whose transfer functions are the complements of the reson opcode.
</p>
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<div class="refsect1" title="Description">
<a id="idp13632272"></a>
<h2>Description</h2>
<p>
A notch filter whose transfer functions are the complements of the reson opcode.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp13619352"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>areson</strong></span> asig, kcf, kbw [, iscl] [, iskip]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp13620480"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>iscl</em></span> (optional, default=0) -- coded scaling factor for resonators. A value of 1 signifies a peak response factor of 1, i.e. all frequencies other than kcf are attenuated in accordance with the (normalized) response curve. A value of 2 raises the response factor so that its overall RMS value equals 1. (This intended equalization of input and output power assumes all frequencies are physically present; hence it is most applicable to white noise.) A zero value signifies no scaling of the signal, leaving that to some later adjustment (see <a class="link" href="balance.html" title="balance"><em class="citetitle">balance</em></a>). The default value is 0.
</p>
<p>
<span class="emphasis"><em>iskip</em></span> (optional, default=0) -- initial disposition of internal data space. Since filtering incorporates a feedback loop of previous output, the initial status of the storage space used is significant. A zero value will clear the space; a non-zero value will allow previous information to remain. The default value is 0.
</p>
</div>
<div class="refsect1" title="Performance">
<a id="idp13672128"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>ares</em></span> -- the output signal at audio rate.
</p>
<p>
<span class="emphasis"><em>asig</em></span> -- the input signal at audio rate.
</p>
<p>
<span class="emphasis"><em>kcf</em></span> -- the center frequency of the filter, or frequency position of the peak response.
</p>
<p>
<span class="emphasis"><em>kbw</em></span> -- bandwidth of the filter (the Hz difference between the upper and lower half-power points).
</p>
<p>
<span class="emphasis"><em>areson</em></span> is a filter whose transfer functions is the complement of <a class="link" href="reson.html" title="reson"><em class="citetitle">reson</em></a>. Thus <span class="emphasis"><em>areson</em></span> is a notch filter whose transfer functions represents the <span class="quote">“<span class="quote">filtered out</span>”</span> aspects of their complements. However, power scaling is not normalized in <span class="emphasis"><em>areson</em></span> but remains the true complement of the corresponding unit. Thus an audio signal, filtered by parallel matching <span class="emphasis"><em>reson</em></span> and <span class="emphasis"><em>areson</em></span> units, would under addition simply reconstruct the original spectrum.
</p>
<p>
This property is particularly useful for controlled mixing of different sources (see <a class="link" href="lpreson.html" title="lpreson"><em class="citetitle">lpreson</em></a>). Complex response curves such as those with multiple peaks can be obtained by using a bank of suitable filters in series. (The resultant response is the product of the component responses.) In such cases, the combined attenuation may result in a serious loss of signal power, but this can be regained by the use of <a class="link" href="balance.html" title="balance"><em class="citetitle">balance</em></a>.
</p>
</div>
<div class="refsect1" title="Examples">
<a id="idp13678816"></a>
<h2>Examples</h2>
<p>
Here is an example of the areson opcode. It uses the file <a class="ulink" href="examples/areson.csd" target="_top"><em class="citetitle">areson.csd</em></a>.
</p>
<div class="example">
<a id="idp13679792"></a>
<p class="title">
<strong>Example 50. Example of the areson opcode.</strong>
</p>
<div class="example-contents">
<p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
<pre class="programlisting">
<span class="csdtag"><CsoundSynthesizer></span>
<span class="csdtag"><CsOptions></span>
<span class="comment">; Select audio/midi flags here according to platform</span>
-odac <span class="comment">;;;RT audio out</span>
<span class="comment">;-iadc ;;;uncomment -iadc if RT audio input is needed too</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o areson.wav -W ;;; for file output any platform</span>
<span class="csdtag"></CsOptions></span>
<span class="csdtag"><CsInstruments></span>
<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">ksmps</span> <span class="op">=</span> 32
<span class="ohdr">nchnls</span> <span class="op">=</span> 2
<span class="ohdr">0dbfs</span> <span class="op">=</span> 1
<span class="oblock">instr</span> 1 <span class="comment">; unfiltered noise</span>
asig <span class="opc">rand</span> 0.5 <span class="comment">; white noise signal.</span>
<span class="opc">outs</span> asig, asig
<span class="oblock">endin</span>
<span class="oblock">instr</span> 2 <span class="comment">; filtered noise</span>
kcf <span class="opc">init</span> 1000
kbw <span class="opc">init</span> 100
asig <span class="opc">rand</span> 0.5
afil <span class="opc">areson</span> asig, kcf, kbw
afil <span class="opc">balance</span> afil,asig <span class="comment">; afil = very loud</span>
<span class="opc">outs</span> afil, afil
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="stamnt">i</span> 1 0 2
<span class="stamnt">i</span> 2 2 2
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
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<p><br class="example-break" />
</p>
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<div class="refsect1" title="See Also">
<a id="idp13682096"></a>
<h2>See Also</h2>
<p>
<a class="link" href="aresonk.html" title="aresonk"><em class="citetitle">aresonk</em></a>,
<a class="link" href="atone.html" title="atone"><em class="citetitle">atone</em></a>,
<a class="link" href="atonek.html" title="atonek"><em class="citetitle">atonek</em></a>,
<a class="link" href="port.html" title="port"><em class="citetitle">port</em></a>,
<a class="link" href="portk.html" title="portk"><em class="citetitle">portk</em></a>,
<a class="link" href="reson.html" title="reson"><em class="citetitle">reson</em></a>,
<a class="link" href="resonk.html" title="resonk"><em class="citetitle">resonk</em></a>,
<a class="link" href="tone.html" title="tone"><em class="citetitle">tone</em></a>,
<a class="link" href="tonek.html" title="tonek"><em class="citetitle">tonek</em></a>
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