I know that this is a very old issue, but it is still relevant as there has not been a solution to it in over 3 years now. But what I am essentially asking for is a Firefox equivalent to the Chrome extension called MuteTab - a way to identify which tabs are making sounds and then mute them accordingly.
Is there a such extension for Firefox? Any other ideas?
This would be especially helpful with websites that sit in the background and then sneak up on you and start making sounds, like with ads. You would have to go through all 100 tabs to find the guilty one and terminate it.
I have noticed that the forum section at Tom's Hardware can start playing embedded videos and make disturbing sound this way when you are not currently viewing tab it's on, even though you have not refreshed the page (although it looks like they automatically refresh the page for you after a given time).
Flashmute and Flashblock are mentioned as alternatives. But they don't really work the same way as MuteTab. Even Mozillazine mentions these tools for in-browser muting of tabs. Trying to download Flashmute only results in
Cannot GET /flashmute.aspx. I don't think it's maintained anymore. And Flashblock completely blocks Flash content.