Comment 18 for bug 77010

Peter, your solution merely causes the computer to ignore alerts by silencing the internal speaker. This is hardly the correct behavior. The correct behavior is for the Gnome Alert sound (which is user customizable) to be played through the active sound device at the times when currently Gnome activates the system beep.

In any case, a user should not have to customize their /etc/modprobe.d/blacklist.conf file just to get a decent experience with Ubuntu.