After reinstalling Alsa due to some mic issues I lost my sound indicator from the Unity service panel. After a bit of Googling I was finally able to piece together the right steps. This post has all the pieces but the selected answer did not work for my situation.
The following steps are what worked for me.
- reinstall indicator-sound
- restart the Unity service panel
I ran the following commands
sudo apt-get install --reinstall indicator-sound
restart unity-panel-service
and my sound indicator returned to the service panel.