官方案例：https://layaair.ldc.layabox.com/demo/?category=2d&group=Sound&name=SimpleDemo
在鼠标移入事件（MOUSE_OVER）里播放音效，没有声音，并且在点击按钮后，会多次播放之前移入事件时的音效，叠加在一起，声音很大。
希望可以做到鼠标移入按钮后播放一个音效，求解决方案。

module laya {
    import Sprite = Laya.Sprite;
    import Stage = Laya.Stage;
    import Text = Laya.Text;
    import Event = Laya.Event;
    import SoundManager = Laya.SoundManager;
    import Browser = Laya.Browser;
    import Handler = Laya.Handler;
    import WebGL = Laya.WebGL; 
    export class Sound_SimpleDemo {
        //声明一个信息文本
        private txtInfo: Text; 
        constructor() {
            // 不支持WebGL时自动切换至Canvas
            Laya.init(Browser.clientWidth, Browser.clientHeight, WebGL); 
            Laya.stage.alignV = Stage.ALIGN_MIDDLE;
            Laya.stage.alignH = Stage.ALIGN_CENTER; 
            Laya.stage.scaleMode = "showall";
            Laya.stage.bgColor = "#232628"; 
            this.setup();
        } 
        private setup(): void {
            var gap: number = 10; 
            //创建一个Sprite充当音效播放按钮
            var soundButton: Sprite = this.createButton("播放音效");
            soundButton.x = (Laya.stage.width - soundButton.width * 2 + gap) / 2;
            soundButton.y = (Laya.stage.height - soundButton.height) / 2;
            Laya.stage.addChild(soundButton); 
            //创建一个Sprite充当音乐播放按钮
            var musicButton: Sprite = this.createButton("播放音乐");
            musicButton.x = soundButton.x + gap + soundButton.width;
            musicButton.y = soundButton.y;
            Laya.stage.addChild(musicButton); 
            soundButton.on(Event.CLICK, this, this.onPlaySound);
            musicButton.on(Event.CLICK, this, this.onPlayMusic);
            //bug在这里：新增鼠标移入后播放音效，无法生效
            soundButton.on(Event.MOUSE_OVER, this, this.onPlaySound);
        } 
        private createButton(label: string): Sprite {
            var w: number = 110;
            var h: number = 40; 
            var button: Sprite = new Sprite();
            button.size(w, h);
            button.graphics.drawRect(0, 0, w, h, "#FF7F50");
            button.graphics.fillText(label, w / 2, 8, "25px SimHei", "#FFFFFF", "center");
            Laya.stage.addChild(button);
            return button;
        } 
        private onPlayMusic(e: Event): void {
            console.log("播放音乐");
            SoundManager.playMusic("../../res/sounds/bgm.mp3", 1, new Handler(this, this.onComplete));
        } 
        private onPlaySound(e: Event): void {
            console.log("播放音效");
            SoundManager.playSound("../../res/sounds/btn.mp3", 1, new Handler(this, this.onComplete));
        } 
        private onComplete(): void {
            console.log("播放完成");
        }
    }
} new laya.Sound_SimpleDemo();