There is a default volume preference for HTML5 media. I don't know if that applies to the notifications you're getting, but I think it's worth a try. (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk. (2) In the search box above the list, type or paste '''VOL''' and pause while the list is filtered (3) Double-click the '''media.default_volume''' preference to display an edit dialog and change '''1.0''' to '''0.5''' and then click OK ''Note that this is global for Firefox media players.'' Does that drop the volume by half?