工具：
Chrome 浏览器
过程：
1、打开Chrome 按F12。会弹出 Developer Tools 窗口。点击 NetWork ，观察访问的网页情况。
2、打开网页：
http:///#/1000202/sound/3613735，点击播放按钮，开始播放音频。
3、此时在 NetWork 输出窗口里会看到各种信息其中有这么一条访问记录
http:///tracks/3613735.json

其返回结果是

复制代码代码如下:
{"id":3613735,"play_path_64":"group4/M08/03/E0/wKgDs1QO0b2jRtupAchYxtSl18g572.mp3","play_path_32":"group4/M07/03/E0/wKgDs1QO0eaSYVN0AOQsfXNp6nQ890.mp3","play_path_128":null,"play_path":"group4/M0A/03/E0/wKgDs1QO0Wjj8YNaBVkpgPW3Atw003.mp3","duration":"3738.72","title":"2010高清 婚姻与家庭（郭德纲 于谦）","nickname":"郭德纲相声","uid":1000202,"waveform":"group4/M08/07/5B/wKgDtFQO0dCjmub2AAAIhDD3SF43160.js","upload_id":"u_3576599","cover_url":"<a href="http://fdfs.xmcdn.com/group4/M07/03/E1/wKgDs1QO0hHBaryDAAGRHqUnuE4210.jpg","cover_url_142":"http://fdfs.xmcdn.com/group4/M07/03/E1/wKgDs1QO0hHBaryDAAGRHqUnuE4210_web_large.jpg","formatted_created_at":"9">http://fdfs.xmcdn.com/group4/M07/03/E1/wKgDs1QO0hHBaryDAAGRHqUnuE4210.jpg","cover_url_142":"http://fdfs.xmcdn.com/group4/M07/03/E1/wKgDs1QO0hHBaryDAAGRHqUnuE4210_web_large.jpg","formatted_created_at":"9</a>月9日 18:10","is_favorited":null,"play_count":27466,"comments_count":49,"shares_count":16,"favorites_count":290,"album_id":276111,"album_title":"郭德纲相声十年经典之五","intro":"郭德纲相声十年经典之五","short_intro":"郭德纲相声十年经典之五","have_more_intro":false,"time_until_now":"16小时前","category_name":"news","category_title":"最新资讯","played_secs":null}

4、而在后面的记录里紧跟着是
http://fdfs.xmcdn.com/group4/M08/03/E0/wKgDs1QO0b2jRtupAchYxtSl18g572.mp3
这就是真正的 Mp3地址了。

总结：

1、请求 http:///tracks/ID.json
2、根据结果里的“play_path_64” 字段使用域名“http://fdfs.xmcdn.com/”拼接得到：http://fdfs.xmcdn.com/group4/M08/03/E0/wKgDs1QO0b2jRtupAchYxtSl18g572.mp3
3、OK！得到 http://fdfs.xmcdn.com/group4/M08/03/E0/wKgDs1QO0b2jRtupAchYxtSl18g572.mp3。
4、一切就是那么简单！