Stop if already playing
<p>I need some assistance implementing the .playing() method, for when my playSound function is called i want to stop anything that is currently playing, and play the newly requested sound, here is my example which is not stopping each time its called:</p>

<pre><code>  function playSound(audio) {
      var playing;
      var sound = new Howl({
        src: ['assets/sound/voice/' + audio],
        autoplay: false,
        volume: 0.9,
        onplay: function() {
          playing = true;
        },
        onend: function() {
          playing = false;
        }          
      });

      if(playing) {
        sound.stop();
      } else {            
        sound.play();      
      }
  }
</code></pre>