Starting to play sound without user confirmation is a default tab-close. I wont even take the time to look at it. Bonus point for not being flash that hijacks the browser shortcut.
Generally I dislike websites that randomly start playing sound (and follow the same tab-close behaviour), but this was not ill-advertised or unexpected.
HN: should I continue to tag those?
I haven't ever submitted anything with autoplaying audio, but I imagine I'd use [autoplay] or similar.
Solving it in the community can solve the problem of people unwittingly stumbling upon it from here, but it doesn't solve the bigger problem, which is that autoplay is rude. (Surely we've all had the experience of not being able to find the tab from the huge group we just opened that's playing the sound.) It's good if sites see that they get fewer visitors with autoplay than without.
I'm not sure there is a good solution to auto-playing. People are fine with it on well-known sites like YouTube, Vimeo, Soundcloud, etc. And most people, when they unwittingly click on a YouTube link, blame the person who made the link, not the site itself. Bizarrely, the target of ire shifts to the site if it's not popular enough.
(Genuine question, as you stated it as a matter of fact. Not trying to be obtuse or annoying.)
You are right about YouTube and I actually think they should handle visitors that come from outside YouTube differently than visitors from inside the site. In the first case auto-play is annoying in the second it is what is wanted.
When I come to HN, I usually read all topics on the front page, then open interesting ones in tabs. After opening 10 tabs, I hear music, then I find the culprit, close the tab, do not look back.
Never play music without user permission.