private function getClass(className:String):Class {

        return loader.contentLoaderInfo.applicationDomain.getDefinition(className) as Class;

}

var loader:Loader = new Loader();

loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onSoundsSwfLoadComplete);

var context:LoaderContext = new LoaderContext(false, ApplicationDomain.currentDomain);

loader.load(new URLRequest("my_sounds.swf"), context);

 

private function onSoundsSwfLoadComplete(event:Event):void

{

    var ClassReference:Class = loader.contentLoaderInfo.applicationDomain.getDefinition("mySound") as Class;

}

loader.load(new URLRequest("my_sounds.swf?t"+new Date().getTime()), context);