Radio noise Puns

My stepfather and mother have been doing some remodeling in their first house to get it ready to put on the market, so they are fixing up some things, and I was giving them a hand. As we were working we had the radio playing.

My mother notices a light switch on the wall in the bedroom that isn't working quite right. She says, "Honey I think there's something wrong with the light switch."

To which my stepfather replies, "What's wrong with it?"

My mother says, "It's making a weird noise. I think it's humming. Why is the light switch humming?"

My stepfather says, "That's probably because it doesn't know the words."