Readline Variables
       Readline has variables that can be used to further customize its behavior.  A variable may be set in the inputrc file with a statement of
       the form
 
              set variable-name value
 
       Except where noted, readline variables can take the values On or Off.  The variables and their default values are:
 
       bell-style (audible)
              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, readline attempts to ring the terminal's bell.