title: AVAudioPlayer change sound URL on the fly
body: <p>In my init method I initialise the sound_a.wav like this. </p>
  
  <pre><code>    AVAudioPlayer *snd = [[AVAudioPlayer alloc] initWithContentsOfURL:[[NSBundle mainBundle] 
      URLForResource:@"sound_a" withExtension:@"wav"] error: nil];
  </code></pre>
  
  <p>Depending on the scenario I need to play a different sound (let's assume that sound is sound_b). </p>
  
  <p>What code do I need to change this on the fly? </p>