The CPU beep is a really irritating thing in Linux distros and sometimes the graphical sound manager does not work when shutting it up.
Fortunately there is a simple way to do it in terminal. In Ubuntu (and distros based upon it) type:
gksudo gedit /etc/modprobe.d/blacklist
In Debian type:
If you are new to Ubuntu, it would be good if you read this Ubuntu, Debian Linux introduction. Its a descriptive explanation regarding Ubuntu, Debian and Linux general. Ubuntu is a Debian based Operating System that is currently become the most popular Linux distribution.
Ubuntu is an operating system based on Debian GNU/Linux (www.debian.org/).
You can knock me over with a feather right at this very moment: Mark Shuttleworth announced in his blog that Ubuntu will follow Debian in adopting systemd as its init system, even though Ubuntu itself coded the alternative Upstart.