问ActionScript 3-播放声音mp3时出现错误

EN

// i have try using this import, but still not work
/*import flash.events.Event;
  import flash.media.Sound;
  import flash.net.URLRequest;
*/

// here is the code
var req:URLRequest=new URLRequest("music.mp3");
var snd:Sound=new Sound();
snd.load(req);
var chan:SoundChannel=snd.play();// not work using 'snd.play(1);' too

chan.addEventListener(Event.SOUND_COMPLETE, onPlaybackComplete); 
function onPlaybackComplete(event:Event){
  trace("Musik Complete");
}

C:/flash/example.fla
C:/flash/example.swf
C:/flash/music.mp3

var Audio:musik = new musik();
var chan:SoundChannel = new SoundChannel();
// play
chan=Audio.play();
// stop
chan.stop();
// i am so confuse i run my friend project and work fine (sound and other), if i write from scrap even i write the same code, there is an error, and this the error:
// 1046: Type was not found or was not a compile-time constant: musik.
// 1180: Call to a possibly undefined method musik.