Sound doesn't work when I load AS2 from AS3

programming flash
1

Hello! I have a AS2 file which I’m loading into an AS3, everything works except the sound, I don’t know why.
These are the lines:

LOAD AS2 from AS3:

 var rect:Shape = new Shape();
 rect.graphics.beginFill(0xFFFFFF);
 rect.graphics.drawRect(0, 0, 800, 600);
 rect.graphics.endFill();
 addChild(rect);
 var ldr:Loader = new Loader();
 ldr.mask = rect;
 var url:String = "file.swf";
 var urlReq:URLRequest = new URLRequest(url);
 ldr.load(urlReq);
 addChild(ldr);

Load Sound from AS2:

var sou:Sound = new Sound();
sou.attachSound("pageturn");
br.onPress=function(){
    sou.start();
}

Does somebody know why I can’t hear the sound when I load it from AS3?

Thanks!
Enrique.