title: playing a sound doesn't work on iPhone
body: <p>I've added a sound to my app. 
  In my .h i've added:</p>
  
  <pre><code>CFURLRef soundFileURL;
  SystemSoundID soundFile;
  </code></pre>
  
  <p>in my viewDidLoad in my .m:</p>
  
  <pre><code>soundFileURL = CFBundleCopyResourceURL(
          CFBundleGetMainBundle(),
          CFSTR("sound"),
          CFSTR("mp3"),
          NULL);
  AudioServicesCreateSystemSoundID(
          soundFileURL,
          &amp;soundFile);
  </code></pre>
  
  <p>and lastly i've added a -playSound method:</p>
  
  <pre><code>-(void)playSound {
  
  NSLog(@"playSound");
  AudioServicesPlayAlertSound(soundFile); }
  </code></pre>
  
  <p>It works fine on the iPhone Simulator, but when I build the app on my iPhone the console says the sound was played but it wasn't. 
  I read that many others had this problem too but I didn't find any solutions.</p>
  
  <p>What's wrong?</p>