I discussed it briefly near the end of the article under "Adding Sounds". The main reason this article doesn't do it is because it's focusing on rendering with canvas, and there's already a lot of information for beginners to go through there.

I plan on writing a followup to include sound, though, or possible extending this article.

What the other comments say is true, also. It's not extremely straightforward. The state of APIs on the web is very mixed, but I think in a year or so the Web Audio API will in most places.