Just add this small script as depicted in https://developers.google.com/web/updates/2017/09/autoplay-policy-changes#webaudio
<head>
<script>
window.onload = function() {
var context = new AudioContext();
}
</script>
</head>
Than this will work as you want:
<audio autoplay>
<source src="hal_9000_sorry_dave.mp3">
</audio>