playbackRate只会使声音变长/变短，如何更改文件的实际音高

Question

所以我有一些代码，

function playRandom() {
  var soundFile = document.getElementById("soundRandom").value;
  var playRate = document.getElementById("soundRandomPitch").value;
  var audio = new Audio(soundFile);
  audio.playbackRate = playRate;
  audio.play();
}

<select id="soundRandom" name="soundRandom"></label>
        		   <option value="sounds/AMBIENCE_CAVE.ogg">Cave</option>
        		   <option value="sounds/BLOCK_BEACON_ACTIVATE.ogg">Beacon Activate</option>
                  </select>

但是playbackRate似乎并没有影响声音的音调，只会使声音变长/变短。我怎样才能真正改变音高和长度？