To enable bash beep command (Fedora Core 15) one have to execute:
yum install beep
chmod 4755 /usr/bin/beep # remove snd-pcsp module from blacklisted ones vi /etc/modprobe.d/blacklist.conf
Now Emacs beeps on errors as well. To disable this feature
one has to add to
(setq visible-bell t)
The error is signaled by a screen flash now (see also [Emacs] AlarmBell).