Mini Audio Icon of Tab - Muted a page then closed it, now I can get audio on any other page. How to I re-enable audio?

This happened once before I mute the sound on a page close the page and or firefox and no other page has sound after that. Also skype and outlook notifications stop working as well. Then it takes me days of reboots and randomly trying things to get it working again. Sound doesn't stop working when i'm talking on skype or whating a video just notifications. Thanks.