How did Battelle know that the strong EMFs that they used caused the hairs on the animals to vibrate? They took high-speed motion pictures and documented the hair vibration. What was the mechanism responsible for the hair vibration? It had something to do with molecules in the air as well as with the EMF. When the Battelle investigators placed a jar over a pig's ear and applied a strong EMF, the hairs on the ear vibrated. When they evacuated the jar so that no air was in contact with the hairs, and then applied the EMF, the hairs did not vibrate.
How did the Battelle investigators know that the animals did not like having their hairs in a continuous state of oscillation? The Battelle investigators did many experiments in which an animal was given a choice regarding which side of the cage it preferred, one of which contained the EMF, and one of which did not. Not surprisingly, the animals preferred not to be in the EMF.