The easiest thing would be to look in wade's source code (in wade.js there is a function called playAudio).
In short, we have 2 different implementations
The one that you are most likely to use is based on the WebAudio API, but there is another one based on plain HTML5 audio that is used where WebAudio is not supported. These days, WebAudio is supported by over 95% of devices.
In the WebAudio implementation, you create a BufferSource and assign it an audio buffer. You then set the loop property of the source to true, connect the source to the WebAudioContext's destination, and start the source:
var audioContext = new AudioContext();
var audioBuffer = wade.getAudio(file);
var source = audioContext.createBufferSource();
source.buffer = audioBuffer;
source.loop = true;