After installing Xfce on my fedora 20 machine. I could not find a volume bar in my panel so I did the following

sudo yum install xfce4-mixer

I then added the following

Pannel >> Add New Items >> Audio Mixer

The Audio Mixer appeared and seems to be working fine. However there is one problem. If I drag the volume bar all the way down the sound goes on mute. Dragging it all the way up then does not unmute the sound. Any suggestions on how I can fix this problem ?