Answer:
You actually can mute an entire tab if your on a Chromebook, here's how:
Press both fingers down on the very top part of the tab (the part that shows even when your on another tab) and click the tab, (again, with both fingers) and then click the "mute site" button. The entire tab will be muted!
Explanation:
I just figured this out for myself and thought I should share it. I hope this makes sense, comment a better way to word it if you have one.
