DisablingBells/Vimperator

Add this to ~/.vimperatorrc:

javascript liberator.beep = function() { return false; }

There's a vb option ("set vb") that replaces the audible bell with a visual bell and a visualbellstyle option that can be set to blank, but when it's set to blank the window still flickers. This is the simplest way I know of to completely remove the bell.