Finally, we get to our original problem with the poor guy and the 5 km farm power line. Turns out this is a simple problem of bell ringing resonance. The line is too tight, and ringing like a bell. You only need a transformer on the line, and the 12 Hz harmonics will do the work.
Solving this might be expensive. Most transmission tower lines now dispense with the Stockbridge damper, by slacking the line a bit. However, the new multi-line arrangement now needs torsional dampers! This farmer could isolate the house from the tight line by putting in a pole to take the tension. Then a loose line to the house would not transmit the infrasonics. It all depends on how much you want to pay.