What's Mallard raving about today?
Metal Detectors, Schools.
Allow me to help, since I am reasonably certain that you are confused at this point.
Rush's father performs an imitation of a metal detector going off.
Rush mistakes this for an impression of his alarm clock and tells his father it is "just mean" to do that to him.
Rush's father says that the word Rush just used to describe his noise-making does not describe his noise-making. Alternately, Rush's father may intend to say that the word "mean" does not do justice to his impression, however, since that's not a qualitative assessment of a metal detector impression, it would be idiotic of him to do so.
In any event, Rush's father has clearly been hit in the head by some sort of blunt object, which finally explains what he has been doing for the past week.