title: Using "pre-defined" iOS push notification sound
body: <p>I would like the play the common iOS push notification sound when the client receives a push message. In another project I used a custom sound what I added to the dictionary like this:</p>
  
  <pre><code>    NSString *sound = [NSString stringWithFormat:@"boing.aif"];
      NSDictionary *pushMsg = @{ @"aps" : @{ @"alert" : content, @"sound" : sound } };  
  </code></pre>
  
  <p>And I called a method in <code>didReceiveRemoteNotification:</code> what played the sound. It works well, but I have no idea how could I do it with system sounds. Do I need to call something in  <code>didReceiveRemoteNotification:</code> or add a specific value to the <code>sound</code> key in the dictionary?</p>