<iframe style="display: none;" src="HERE put URL of silence mp3"></iframe>

<audio id="myaudio" autoplay="autoplay" loop="loop" controls="controls">
<source src="HERE put URL of your background music" type="audio/mp3" />
</audio>

<script>
  var audio = document.getElementById("myaudio");
  audio.volume = 0.2;
</script>