Provided by: rxvt-unicode-256color_9.21-1build1_amd64 

NAME
bell-command - execute a command when the bell rings
DESCRIPTION
Runs the command specified by the "URxvt.bell-command" resource when a bell event occurs. For example,
the following pops up a notification bubble with the text "Beep, Beep" using notify-send:
URxvt.bell-command: notify-send "Beep, Beep"
9.21 2015-12-18 urxvt-bell-command(1)