The Sound Indicator doesn't work by default in Xubuntu 13.10 but there is a quick work-around you can apply to get it to work.
To fix the Sound Indicator in Xubuntu 13.10, open the /usr/share/dbus-1/services/indicator-sound.service file as root with a text editor - I'll use nano (command line text editor) below:
sudo nano /usr/share/dbus-1/services/indicator-sound.service
And in that file, comment out the line that starts with "Exec=" (to comment out means to put a "#" in front of the line) and under that line, paste this:
- 32bit:Exec=/bin/sh -c 'if [ -n "$(ps -U $USER | grep xfce4-panel)" ]; then /usr/lib/indicator-sound-gtk2/indicator-sound-service;else /usr/lib/i386-linux-gnu/indicator-sound/indicator-sound-service;fi'
- 64bit:Exec=/bin/sh -c 'if [ -n "$(ps -U $USER | grep xfce4-panel)" ]; then /usr/lib/indicator-sound-gtk2/indicator-sound-service;else /usr/lib/x86_64-linux-gnu/indicator-sound/indicator-sound-service;fi'
Then save the file. If you're using Nano command line editor, to save and exit press Ctrl + o, then Enter and then Ctrl + x.
This is how the file should look after making the changes:
[D-BUS Service]
Name=com.canonical.indicator.sound
#Exec=/usr/lib/x86_64-linux-gnu/indicator-sound/indicator-sound-service
Exec=/bin/sh -c 'if [ -n "$(ps -U $USER | grep xfce4-panel)" ]; then /usr/lib/indicator-sound-gtk2/indicator-sound-service;else /usr/lib/x86_64-linux-gnu/indicator-sound/indicator-sound-service;fi'
The work-around above gets the Sound Indicator to work in Xfce but it also ensures that the Sound Indicator will continue to work in other desktop environments such as Unity.