So wait...
Why didn't Frankie (Michael Alaimo) hear Tony (Kevin Nealon) shouting and moving around in the back of his truck? Are we really expected to believe he couldn't hear all that noise just because he was singing to himself?!?
shareFrankie was deaf. That's why when the Dad or the kids were speaking to him they were shouting....
Also the Dad actually says "He's deaf as a post"