juniorÉn is azt hittem először, hogy ennyi, de nem, mivel a notification area-hoz tartozik.
Itt a megoldás:
Use Alt+F2 to open the Run Application app, paste gnome-volume-control-applet into the text field, and click the Run button (you can also enter the command into a terminal, but the button will disappear if you close the terminal). To get it to start automatically from the next reboot, go to System > Preferences > Startup Applications and add it as a new entry with a name like “Volume Button”.