code: function loadArrayBuffer() {
          if (url instanceof window.ArrayBuffer) {
              decodeArrayBuffer(url);
              return;
          }
          request = new XMLHttpRequest();
          request.open('GET', url, true);
          request.responseType = 'arraybuffer';
          request.addEventListener('progress', progressHandler);
          request.addEventListener('load', loadHandler);
          request.addEventListener('error', errorHandler);
          request.send();
      }
docs: audio buffer