While I dislike websites playing sudden sounds as much as the next guy, it should serve as a reminder to keep your computer muted at all times or have a pair of headphones plugged in when you share office space.
If I ever go postal in the open plan office here, then it's going to be over random noise (skype sounds being the worst culprit) escaping someone's unmuted laptop.
I'm very annoyed about the sudden blaring, jarring music. Got a few angry stares from colleagues.
The polite thing to have done would at least put up a notice.