Imagine you have a tab open somewhere in the background playing music. Now, in your current tab, you start playing a video. Smart Tab Mute will automatically mute the background tab, and unmute it again once the video has finished playing.
Like the original Chrome extension this add-on supports a whitelist of domains which will never be muted (useful for sites using audio notifications like chats etc.). Currently this whitelist contains slack.com and messenger.com. With the next version of Firefox (48, scheduled for August 2016) it will be possible to customize this whitelist.
