areson.xml

<refentry id="areson">
<indexterm id="IndexAreson"><primary>areson</primary></indexterm>
  <refentryinfo><title>Signal Modifiers:Standard Filters:Resonant</title></refentryinfo>
  <refmeta>
    <refentrytitle>areson</refentrytitle>
  </refmeta>


 
  <refnamediv>
    <refname>areson</refname>
    <refpurpose>
      A notch filter whose transfer functions are the complements of
      the reson opcode. 
    </refpurpose>
  </refnamediv>
 
  <refsect1>
    <title>Description</title>
    <para>
      A notch filter whose transfer functions are the complements of
      the reson opcode. 
    </para>
  </refsect1>
 
  <refsect1>
    <title>Syntax</title>
    <synopsis>ares <command>areson</command> asig, kcf, kbw [, iscl] [, iskip]</synopsis>
    <synopsis>ares <command>areson</command> asig, acf, kbw [, iscl] [, iskip]</synopsis>
    <synopsis>ares <command>areson</command> asig, kcf, abw [, iscl] [, iskip]</synopsis>
    <synopsis>ares <command>areson</command> asig, acf, abw [, iscl] [, iskip]</synopsis>
  </refsect1>
 
  <refsect1>
    <title>Initialization</title>
    <para>
      <emphasis>iscl</emphasis> (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 <link
      linkend="balance"><citetitle>balance</citetitle></link>). The
      default value is 0. 
    </para>

    <para>
      <emphasis>iskip</emphasis> (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.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Performance</title>
    <para>
      <emphasis>ares</emphasis> -- the output signal at audio rate.
    </para>

    <para>
      <emphasis>asig</emphasis> -- the input signal at audio rate.
    </para>

    <para>
      <emphasis>kcf</emphasis>/<emphasis>acf</emphasis>  -- the center
      frequency of the filter, or frequency position of the peak
      response. 
    </para>

    <para>
      <emphasis>kbw</emphasis>/<emphasis>abw</emphasis> -- bandwidth
      of the filter (the Hz difference between the upper and lower
      half-power points). 
    </para>

    <para>
      <emphasis>areson</emphasis> is a filter whose transfer functions
      is the complement of <link
      linkend="reson"><citetitle>reson</citetitle></link>. Thus
      <emphasis>areson</emphasis> is a notch filter whose transfer
      functions represents the <quote>filtered out</quote> aspects of
      their complements. However, power scaling is not normalized in
      <emphasis>areson</emphasis> but remains the true complement of
      the corresponding unit. Thus an audio signal, filtered by
      parallel matching <emphasis>reson</emphasis> and
      <emphasis>areson</emphasis> units, would under addition simply
      reconstruct the original spectrum.
    </para>

    <para>
      This property is particularly useful for controlled mixing of
      different sources (see <link
      linkend="lpreson"><citetitle>lpreson</citetitle></link>). 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
      <link linkend="balance"><citetitle>balance</citetitle></link>.
    </para>
    <para>
      <warning> When used with <emphasis>iscl</emphasis> this opcode
      is not a notch filter but similar to <link
      linkend="reson"><citetitle>reson</citetitle></link>.
      </warning>
    </para>
  </refsect1>

  <refsect1>
    <title>Examples</title>
    <para>
      Here is an example of the areson opcode. It uses the file <ulink url="examples/areson.csd"><citetitle>areson.csd</citetitle></ulink>.

      <example>
        <title>Example of the areson opcode.</title>
        

        <para>See the sections <link linkend="UsingRealTime"><citetitle>Real-time Audio</citetitle></link> and <link linkend="CommandFlags"><citetitle>Command Line Flags</citetitle></link> for more information on using command line flags.</para>
          <xi:include href="examples-xml/areson.csd.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
      </example>
    </para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <link linkend="aresonk"><citetitle>aresonk</citetitle></link>, 
      <link linkend="atone"><citetitle>atone</citetitle></link>, 
      <link linkend="atonek"><citetitle>atonek</citetitle></link>, 
      <link linkend="port"><citetitle>port</citetitle></link>, 
      <link linkend="portk"><citetitle>portk</citetitle></link>, 
      <link linkend="reson"><citetitle>reson</citetitle></link>, 
      <link linkend="resonk"><citetitle>resonk</citetitle></link>, 
      <link linkend="tone"><citetitle>tone</citetitle></link>, 
      <link linkend="tonek"><citetitle>tonek</citetitle></link>
    </para>
  </refsect1>

  <refsect1>
    <title>Credits</title>
    <para>Audio rate parameters introduced in version 6.02</para>
    <para>October 2013.</para>
  </refsect1>
</refentry>