XMLHttpRequest :: audio加载失败

Question

我正在使用python SimpleHTTPServer在localhost上投放测试页。

src标记的空audio。

<audio id="audio" src=" "></audio>

请求：

<script>
var request = new XMLHttpRequest();
request.open("GET", "http://127.0.0.1:8000/audio/song.wav", true);
request.responseType = "blob";    
request.onload = function() {
  if (this.status == 200) {
    var audio = document.getElementById("audio");
    var src = URL.createObjectURL(this.response);
    audio.src = src;
    audio.load();
    audio.play();
  }
}
request.send();
</script>

但XHR加载失败。错误在哪里？