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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>
</div>
<div class="refsect1">
<a id="idm281472951362312"></a>
<h2>Description</h2>
<p>
A notch filter whose transfer functions are the complements of
the reson opcode.
</p>
</div>
<div class="refsect1">
<a id="idm281472951360888"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>areson</strong></span> asig, kcf, kbw [, iscl] [, iskip]</pre>
<pre class="synopsis">ares <span class="command"><strong>areson</strong></span> asig, acf, kbw [, iscl] [, iskip]</pre>
<pre class="synopsis">ares <span class="command"><strong>areson</strong></span> asig, kcf, abw [, iscl] [, iskip]</pre>
<pre class="synopsis">ares <span class="command"><strong>areson</strong></span> asig, acf, abw [, iscl] [, iskip]</pre>
</div>
<div class="refsect1">
<a id="idm281472951314392"></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/acf 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">
<a id="idm281472951308984"></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>/<span class="emphasis"><em>acf</em></span> -- the center
frequency of the filter, or frequency position of the peak
response.
</p>
<p>
<span class="emphasis"><em>kbw</em></span>/<span class="emphasis"><em>abw</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>
<p>
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
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<td rowspan="2" align="center" valign="top" width="25">
<img alt="[Warning]" src="images/warning.png" />
</td>
<th align="left">Warning</th>
</tr>
<tr>
<td align="left" valign="top"> When used with <span class="emphasis"><em>iscl</em></span> this opcode
is not a notch filter but similar to <a class="link" href="reson.html" title="reson"><em class="citetitle">reson</em></a>.
</td>
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</table>
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<p>
</p>
</div>
<div class="refsect1">
<a id="idm281472951293384"></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="idm281472951291608"></a>
<p class="title">
<strong>Example 56. 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>
<div class="refsect1">
<a id="idm281472786634776"></a>
<pre class="programlisting">
<span class="nt"><CsoundSynthesizer></span>
<span class="nt"><CsOptions></span>
<span class="c1">; Select audio/midi flags here according to platform</span>
-odac <span class="c1">;;;RT audio out</span>
<span class="c1">;-iadc ;;;uncomment -iadc if RT audio input is needed too</span>
<span class="c1">; For Non-realtime ouput leave only the line below:</span>
<span class="c1">; -o areson.wav -W ;;; for file output any platform</span>
<span class="nt"></CsOptions></span>
<span class="nt"><CsInstruments></span>
<span class="vg">sr</span> <span class="o">=</span> <span class="mi">44100</span>
<span class="vg">ksmps</span> <span class="o">=</span> <span class="mi">32</span>
<span class="vg">nchnls</span> <span class="o">=</span> <span class="mi">2</span>
<span class="vg">0dbfs</span> <span class="o">=</span> <span class="mi">1</span>
<span class="kd">instr</span> <span class="nf">1</span> <span class="c1">; unfiltered noise</span>
a<span class="n">sig</span> <span class="nb">rand</span> <span class="mf">0.5</span> <span class="c1">; white noise signal.</span>
<span class="nb">outs</span> a<span class="n">sig</span><span class="p">,</span> a<span class="n">sig</span>
<span class="kd">endin</span>
<span class="kd">instr</span> <span class="nf">2</span> <span class="c1">; filtered noise</span>
k<span class="n">cf</span> <span class="nb">init</span> <span class="mi">1000</span>
k<span class="n">bw</span> <span class="nb">init</span> <span class="mi">100</span>
a<span class="n">sig</span> <span class="nb">rand</span> <span class="mf">0.5</span>
a<span class="n">fil</span> <span class="nb">areson</span> a<span class="n">sig</span><span class="p">,</span> k<span class="n">cf</span><span class="p">,</span> k<span class="n">bw</span>
a<span class="n">fil</span> <span class="nb">balance</span> a<span class="n">fil</span><span class="p">,</span>a<span class="n">sig</span> <span class="c1">; afil = very loud</span>
<span class="nb">outs</span> a<span class="n">fil</span><span class="p">,</span> a<span class="n">fil</span>
<span class="kd">endin</span>
<span class="nt"></CsInstruments></span>
<span class="nt"><CsScore></span>
<span class="nb">i</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">2</span>
<span class="nb">i</span> <span class="mi">2</span> <span class="mi">2</span> <span class="mi">2</span>
<span class="nb">e</span>
<span class="nt"></CsScore></span>
<span class="nt"></CsoundSynthesizer></span>
</pre>
</div>
</div>
</div>
<p><br class="example-break" />
</p>
</div>
<div class="refsect1">
<a id="idm281472951287368"></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>
</p>
</div>
<div class="refsect1">
<a id="idm281472951277576"></a>
<h2>Credits</h2>
<p>Audio rate parameters introduced in version 6.02</p>
<p>October 2013.</p>
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