Development Flash ActionScript

package {
    import flash.display.Sprite;
    import flash.media.Sound;
    import flash.media.SoundChannel;
    import flash.net.URLRequest;
    import flash.events.Event;
    public class ProgressBar2 extends Sprite {
        private var _sound:Sound;
        private var _channel:SoundChannel;
        
        public function ProgressBar2(  ) {
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
            _sound = new Sound(new URLRequest("song.mp3"));
            _channel = _sound.play(  );
        }
        
        public function onEnterFrame(event:Event):void
        {
           
            var loaded:int = _sound.bytesLoaded;
            var total:int = _sound.bytesTotal;
            
            var length:int = _sound.length;
            var position:int = _channel.position;
            
            if(total > 0) {
               trace(loaded);
               trace(length);
               trace(position);
            }
        }
    }    
}