Hi   ! The default Firefox notification system doesn't notify you with audio, only visually. So, my guess is that it's your OS that's being 'noisy' : https://www.imore.com/how-enable-and-disable-notification-sounds-your-mac Also : http://osxdaily.com/2015/03/31/stop-messages-sound-effects-playing- mac-os-x/ Unless you happen to have this add-on installed and forgot all about it : https://addons.mozilla.org/en-US/firefox/addon/notification-sound/ ---------------------------------------------------------------------------------------------------------- Separate issue : Your system details show that your Flash needs to be updated : Uninstall Flash for Mac OS : https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html Downwload Flash for other systems : https://get.adobe.com/flashplayer/otherversions/