title: How do I know the duration of a sound in Web Audio API
body: <p>It's basicly all in the title, how do I know or how can I access the duration of a soundNode in Web Audio API. I was expecting something like <code>source.buffer.size</code> or <code>source.buffer.duration</code> to be available. </p>
  
  <p>The only alternative I can think of in case this is not possible to acomplish is to read the file metadata.</p>