flash内置类Sound的一个小问题及解决方法

var _tmp;
var s1_sound = new Sound();
var s2_sound = new Sound();
s1_sound.attachSound("s1");
s2_sound.attachSound("s2");
s1_sound.start(0,1000);
_btn.onPress = function(){
_tmp = !_tmp;
if(_tmp){
s2_sound.start();
} else {
s2_sound.stop();
}
}

var _tmp;
var s1_sound = new Sound();
var s2_sound = new Sound();
s1_sound.onLoad = function(){
this.start();
}
s1_sound.loadSound("s1.mp3");
s2_sound.loadSound("s2.mp3");
_btn.onPress = function(){
_tmp = !_tmp;
if(_tmp){
s2_sound.start();
} else {
s2_sound.stop();
}
}