playbackRate

After watching this Best of #DrunkDonaldTrump - YouTube

Normal 1.0
Drunk 0.5

<script type="text/javascript">
		var voice = document.getElementById("myAudio");
		voice.playbackRate = 0.5;
	
		function setspeed(s){
			var voice = document.getElementById("myAudio");
			voice.playbackRate = s;
		
		}
	</script>