Riddle Me This Batman; Low Frequency Hum: SOLVED

Once worked in a office with open floor plan where roof was supported by the metal stancions. Fellow employee who played in college band and had advanced degrees in music said one of the stancions near his desk hummed. He claimed it was so loud he had to relocate. No one else in the office could hear it. Management had it checked out and sure you he was right. We were not interested in why it hummed...