Google Chrome has changed its autoplay policy in the past few years [0] -- sites now require typically user interaction before they're allowed to start the audio context.

You can see this in the page's code [1] -- line 157 and further.

I was surprised to hear the page start playing right away though. Maybe Chrome's "whitelisting" has become more permissive..? See this [2] as well.

[0] https://developers.google.com/web/updates/2017/09/autoplay-p...

[1] http://listen.hatnote.com/

[2] https://developer.mozilla.org/en-US/docs/Web/Media/Autoplay_...