The problem appears to be to do with PulseAudio. There are many threads about this on the forums.
http://ubuntuforums.org/showpost.php?p=5272022&postcount=10 -- There is no logoff sound https://bugs.launchpad.net/bugs/243238 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs