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[edit] Globally

• You can completely disable the PC speaker module at startup by adding !pcspkr to the MODULES array in /etc/rc.conf:

MODULES=( ... !pcspkr ... )

• If lsmod | grep snd_pcsp returns something, add !snd_pcsp:

MODULES=( ... !snd_pcsp ... )

[edit] Locally

• To disable the annoying PC speaker beep in X:

$ xset -b

You can add this command to a startup file, such as ~/.xinitrc, to disable it every time X starts.

• To disable it in console:

$ setterm -blength 0

Similarly you can add it to ~/.bashrc.

• Another way is to add this line to ~/.inputrc:

set bell-style none

• ALSA users can also try muting the PC Speaker:

$ amixer set 'PC Speaker' 0% mute

Have a look at these man pages for further information: xset(1), setterm(1), readline(3)