<!-- Converted to DocBook/SGML by Kevin Conder -->
<refentry id="noise">
  <refmeta>
    <refentrytitle>noise</refentrytitle>
  </refmeta>
 
  <refnamediv>
    <refname>noise</refname>
    <refpurpose>
      A white noise generator with an IIR lowpass filter.
      <indexterm id="IndexNoise"><primary>noise</primary></indexterm>
    </refpurpose>
  </refnamediv>
 
  <refsect1>
    <title>Description</title>
    <para>
      A white noise generator with an IIR lowpass filter.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Syntax</title>
    <synopsis>ar <command>noise</command> xamp, kbeta</synopsis>
  </refsect1>
 
  <refsect1>
    <title>Initialization</title>
    <para>
      <emphasis>ioffset</emphasis> -- the delay before the first impulse. If it is negative, the value is taken as the number of samples, otherwise it is in seconds. Default is zero.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Performance</title>
    <para>
      <emphasis>xamp</emphasis> -- amplitude of final output
    </para>

    <para>
      <emphasis>kbeta</emphasis> -- beta of the lowpass filter. Should be in the range of 0 to 1.
    </para>

    <para>
      The filter equation is:

      <literallayout>
y_n = sqrt(1-beta^2) * x_n + beta Y_(n-1)
      </literallayout>

      where <emphasis>x_n</emphasis> is white noise.
    </para>
  </refsect1>

  <refsect1>
    <title>Examples</title>
    <para>
      Here is an example of the noise opcode. It uses the files <ulink url="examples/noise.orc"><citetitle>noise.orc</citetitle></ulink> and <ulink url="examples/noise.sco"><citetitle>noise.sco</citetitle></ulink>.

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

        <programlisting>
<inlinemediaobject>
            <imageobject>
              <imagedata fileref="examples/noise.orc" format="linespecific">
            </imageobject>
          </inlinemediaobject>
        </programlisting>

        <programlisting>
<inlinemediaobject>
            <imageobject>
              <imagedata fileref="examples/noise.sco" format="linespecific">
            </imageobject>
          </inlinemediaobject>
        </programlisting>
      </example>
    </para>
  </refsect1>
 
  <refsect1>
    <title>Credits</title>
    <para>
      <simplelist>
        <member>Author: &namejohn;</member>
        <member>University of Bath, Codemist. Ltd.</member>
        <member>Bath, UK</member>
        <member>December 2000</member>
      </simplelist>
    </para>
    <para>Example written by &namekevin;.</para>

    <para>New in Csound version 4.10</para>
  </refsect1>
</refentry>
