title: How to dectect silence in AVAudioRecorder?
body: <p>I use AVAudioRecorder for voice recording. Currently I use <code>averagePowerForChannel</code> and <code>peakPowerForChannel</code> to show a dynamic meter. </p>
  
  <p>How can I detect silence (no body speaks for 1 second) and so I can stop the recording?</p>