I guess this sort of thing is not prevented because possibly some people will deliberately use such a facility to play background music. I am not aware here is any method to easily locate such a tab, however you can use script or flash blockers to prevent tabs playing music or video. Or even simpler, if the adverts happen to use FlashPlayer; as is likely; it should be possible to ensure the site concerned does not use FlashPlayer by default, and that would prevent it from playing FlashPlayer audio and could alleviate or remove the nuisance. * [[Why do I have to click to activate plugins?]]