Which version of ubuntu, your user CP says 9.04, which is no longer supported. However, aside from this I seem to remember a shutdown beep which was a bug in a previous version of ubuntu, maybe 9.04, but I can't remember which.
I have just remembered that I made a txt file to remind myself of the bug's solution, which is this:-
Stop Anoying Shutdown Beep!
the file system in jaunty has changed slightly and the command will manually add "blacklist pcspkr" to the file /etc/modprobe.d/blacklist.conf
It worked for me and many others
echo 'blacklist pcspkr' | sudo tee -a /etc/modprobe.d/blacklist.conf