Perfect!!
There seems to have been a surge these days, in my country at least, of websites, even professional ones relating to stuff like financial services, etc., to have a "May I help you?" kinda helper bots pop up with an audible ding every time you access their webpages. It gets very tedious after a while.
This add-on is exactly what I needed! Well done, developer! Having a whitelist means I can easily and permanently unmute websites like youtube, etc.
My one nitpick is that there should be an option to hide the muted audio icon on each and every tab that is open. Someone like me who has tens of tabs open at a given time, it can look very crowded. I hope the developer take this into consideration for a future update. Else, perfect!
EDIT: I noticed that Developer has replied to another review regarding the audio icon, and suggested editing the userchrome.css to achieve the same. While this worked for me in regular tabs, it did not remove the icons from pinned tabs. Maybe developer can help me in this regard.