Chrome: We've all been there -- you open a site in a new tab, and it starts playing audio in the background. Or worse, you open it in the foreground and it starts a video in some random corner of the page while you read an article. Silent Site Sound Blocker puts an end to that nonsense for good. Once installed, Silent Site Sound Blocker only allows whitelisted sites to play audio. When you visit a site that tries to auto-play audio or a video, you get a pop-over asking whether you'd like to whitelist the site and play audio from it all the time, play it just this once and then ask the next time you visit, reject this once and ask the next time you visit, or blacklist the site entirely and never play audio when you visit it again. That latter one is perfect for those news sites that always seem to have a tiny video somewhere on the page that starts playing as soon as the page loads, or worse, plays anyway even after you click pause to stop it.
The extension is simple, and a labour of love from one developer who considers it a bit of a public beta. You can just as easily configure the tool to work on a blacklist model instead of a whitelist one -- just right-click on the toolbar to switch modes. Best of all, he's open and receptive to feedback and feature requests (he mentioned a "quiet hours" option where audio would only ever play during certain times, which I think would be quite useful). Hit the link below to try it out yourself.
Silent Site Sound Blocker [Chrome Web Store]