I am familiar with the basic theory of how lightning rods work, at least as explained in the text "Electromagnetics" by Kraus (Ohio State). I was once standing on the roof of a 14-story dormitory at the U. of Illinois, Champaign-Urbana. A thunderstorm was approaching. The lightning rods on the roof all began to buzz. I was taking a course in electromagnetic fields at the time. I related the buzzing to the prof, but he had no explanation. Can anybody explain this ? I suppose the ambient 60 Hz field from the power company could be implicated somehow. Thank you.