adicione set bell-style none
ao arquivo init readline, ~ / .inputrc
bell-style
Controls what happens when Readline wants to ring the terminal bell. If set to ‘none’, Readline never rings the bell. If set to ‘visible’, Readline uses a visible bell if one is available. If set to ‘audible’ (the default), Readline attempts to ring the terminal's bell.the terminal's bell.
[editar: obrigado Fedyashev Nikita]