[silin]

запустить интервал с проверкой текущего времени, например

time = new Date();
time_s = time.getSeconds();
time_m = time.getMinutes();
time_h = time.getHours();
function playSound(){
	var currentTime=new Date();
	var curr_h=currentTime.getHours(),curr_m=currentTime.getMinutes(),curr_s=currentTime.getSeconds();
	if (curr_h!=time_h){
		trace("H");//играем 'часовой' звук
		time_h=curr_h;
		time_m=curr_m;
		time_s=curr_s;
		return;
	}
	if(curr_m!=time_m){
		trace("M");//играем 'минутовый' звук
		time_m=curr_m;
		time_s=curr_s;
		return;
	}
	if(curr_s!=time_s){
		trace("S:"+curr_s);
		time_s=curr_s;
	}
}
setInterval(playSound,50);