This has been driving me crazy for a while, but I never did anything about it: Whenever I use the keyboard to delete a file in the file manager using the DEL key, or go back a directory using BACKSPACE, or some everyday task like that, the computer beeps really loud, and almost makes me jump out of my chair. Disabling the speaker in ALSA Mixer does not work, and setting the volume to zero also does not help. So here is how to get rid of that beep:
In a terminal, write:
$ xset -bYou can of course also put this in your startup script (.bashrc or something) to make it permanent.
From the Bottom of my heart I thank you.
The Beep is finnaly gone