A member of Google's Chrome development team announced today that it's working on a mute button for websites. In a post, François Beaufort said, "This will give you more control about which website is allowed to throw sound at you automatically."
Chrome already lets you mute tabs, but once you leave the site you've muted, the setting is undone. This option would let you mute websites for repeated visits until you decide to unmute them. You can try the feature out in Chrome's experimental Canary version by clicking on the "Secure" button to the left of the address bar and turning off the sound toggle in the page info menu that pops up.
Apple is also working on a function that would keep unwanted sound from automatic videos in check. For it's upcoming High Sierra desktop OS, the updated Safari browser will give users the option to keep auto-play videos paused until they decide they want them to play.
Chrome's mute feature is currently in testing.