You want to know more about the "Bark when Blocked" feature of K9 Web Protection.
If you enable the "Bark when blocked" setting on the Blocking Effects page, you will hear an audible bark each time a website is blocked. This feature is useful to alert a parent, teacher, or other care provider that someone under his or her supervision might be stumbling onto offensive or inappropriate content.
NOTE: You must have speakers connected to your computer, and the volume control must not be set to “mute” or you will not hear the bark.
If you are getting excessive barks, or barks without block pages, please upgrade to K9 Web Protection 4.2.x or later.