title: How do I convert a wav file to mp3 format using sox?
body: <p>When I run sox directly from the command line as ;</p>
  
  <pre><code>sox -r 8000 -c 1 &lt;wavfilename&gt; &lt;mp3filename&gt;
  </code></pre>
  
  <p>I get the following error message:</p>
  
  <blockquote>
    <p>sox: Unknown output file format for
    '747a.mp3':  File type 'mp3' is not
    known</p>
  </blockquote>
  
  <p>My machine is running the CentOS operating system.</p>