The Reddit thread can be found here: http://www.reddit.com/r/reddit.com/comments/j5bl3/can_whoever_makes_browsers_please_consider_adding/
The extension itself is located here: http://www.mutetab.com/
Basically, my project is a Chrome extension that attempts to provide browser-wide sound management to the extent possible within an extension. It helps a user find what is making sound by identifying what is possibly making sound, allows automatically muting background sounds, and provides a context menu with sound management commands that will use JavaScript where available and otherwise hides elements from the page.
It does not solve the more general "mute tab" problem -- if a plugin instance doesn't have a JavaScript API, then the only way I can mute it is by hiding it from the page (like Flashblock does). This is unideal because if it is a game or a video, hiding and reshowing it will restart it.
I'm most interested in getting technical feedback (please read the FAQ since I mention some ideas that I haven't heard anyone discuss) but am also interested in feedback about how I am presenting things (what I'm doing might be too complicated for many users to understand) and general feedback.