loadBuffer = function(self) {
    var url = self._src;

    // Check if the buffer has already been cached and use it instead.
    if (cache[url]) {
      // Set the duration from the cache.
      self._duration = cache[url].duration;

      // Load the sound into this Howl.
      loadSound(self);

      return;
    }

    if (/^data:[^;]+;base64,/.test(url)) {
      // Decode the base64 data URI without XHR, since some browsers don't support it.
      var data = atob(url.split(',')[1]);
      var dataView = new Uint8Array(data.length);
      for (var i=0; i<data.length; ++i) {
        dataView[i] = data.charCodeAt(i);
      }

      decodeAudioData(dataView.buffer, self);
    } else {
      // Load the buffer from the URL.
      var xhr = new XMLHttpRequest();
      xhr.open(self._xhr.method, url, true);
      xhr.withCredentials = self._xhr.withCredentials;
      xhr.responseType = 'arraybuffer';

      // Apply any custom headers to the request.
      if (self._xhr.headers) {
        Object.keys(self._xhr.headers).forEach(function(key) {
          xhr.setRequestHeader(key, self._xhr.headers[key]);
        });
      }

      xhr.onload = function() {
        // Make sure we get a successful response back.
        var code = (xhr.status + '')[0];
        if (code !== '0' && code !== '2' && code !== '3') {
          self._emit('loaderror', null, 'Failed loading audio file with status: ' + xhr.status + '.');
          return;
        }

        decodeAudioData(xhr.response, self);
      };
      xhr.onerror = function() {
        // If there is an error, switch to HTML5 Audio.
        if (self._webAudio) {
          self._html5 = true;
          self._webAudio = false;
          self._sounds = [];
          delete cache[url];
          self.load();
        }
      };
      safeXhrSend(xhr);
    }
  }
Buffer a sound from URL, Data URI or cache and decode to audio source (Web Audio API).
@param  {Howl} self