Well, they have examples of how magnetic fields flow from watching the sun's photosphere and corona, the auroras. Experiments with iron filings and whatnot. Using mathematics etc. and field meters around various devices and equipment. The visualization was not even close to exact, but was very accurate in terms of how such a field would look and how they'd move.
The noises were real, the "whistlers" are the sounds of electrons flowing within magnetic field lines.