Remove _ringtone and _vibrate from `Notification` and make them function declarations within the IIFE scope:

```js

function ringtone(tonefile) {
  var audio = new Audio();
  audio.src = tonefile;
  audio.mozAudioChannelType = 'notification';

  audio.onplay = function() {
    audio.onplay = null;
    window.setTimeout(function ringtoneEnd() {
      audio.pause();
      audio.src = '';
    }, 2000);
  };

  audio.play();
}

function vibrate() {
  // vibration only works when App is in the foreground
  if (document.mozHidden) {
    window.addEventListener('mozvisibilitychange', function waitOn() {
      window.removeEventListener('mozvisibilitychange', waitOn);
      navigator.vibrate([200, 200, 200, 200]);
    });
  } else {
    navigator.vibrate([200, 200, 200, 200]);
  }
}
```