You are working alone in a dank and dark room. A little dehydrated and hungry, you have been too immersed in your work to notice. The room is dimly lit and warm but thankfully has a ventilating fan that’s a little noisy, but works okay.
As you yawn and stretch, you feel a sudden presence around you. The hairs on the back of your neck stand up. You see a dim gray figure in front of you. As you rub your eyes and squint, the figure continues to hover above the ground and started to move towards you.
That was what Vic Tandy experienced one day in 1998. However, instead of soiling his pants, he did a little investigating and found that the room he was in has an extractor fan whose blade was swinging at a low freuquency of 18.98 hertz–the exact frequency at which a human eyeball starts resonating. The resultant resonance produced an optical illusion
Ghost sightings has been associated with the presence of so-called infrasound. Animals respond to infrasonic signals during an earthquake and were witnessed fleeing an area before disaster hits. The human ear is not able to process sound waves below 20Hz but some people are prone to the effects of infrasonic waves nonetheless. A scientific experiment was carried out where an audience listened to live music pieces laced with infrasound.
The unusual experiences reported included feeling uneasy or sorrowful, getting chills down the spine or nervous feelings of revulsion or fear.