MuteTab is a Chrome extension that helps you manage the sound coming from tabs in Google Chrome. It helps you to narrow down which tab(s) are making sounds and provides browser-wide management of tab muting (pausing YouTube, HTML5 Video/Audio, and QuickTime and stopping others), including automatically muting all background tabs(*).
It does not, however, universally allow muting a video or game so that it can be played silently while listening to background sounds coming from another tab. (This is not possible in Chrome without plug-ins such as Flash being updated and Chrome's plug-in architecture undergoing a major redesign.) Also, like other extensions, it unfortunately does not work on tabs that were opened prior to installing it.
* There are a few ways that your browser can make sound that are not detectable; see the FAQ for further information.
Created by Jared Sohn. Feel free to contact me with questions or issues (but please try to check the FAQ, documentation, and extension description in the webstore first) at mutetabextension at gmail.com or @mutetab on Twitter.