[silin]

надо слушать SOUND_COMPLETE soundControl'a
можно так:

function playSound(event:MouseEvent):void
{
	soundControl = sound.play();
	soundControl.addEventListener(Event.SOUND_COMPLETE, stopSound);
	play_btn.visible = false;
	stop_btn.visible = true;
}
 
function stopSound(event:Event):void
{
	soundControl.stop();
	stop_btn.visible = false;
	play_btn.visible = true;
}