Purpose: To explain what infra sound is and what effects it can have on the human body and possibilities of paranormal event!
In 1998, computer specialist Vick Tandy from Coventry University always spent a lot of time in his laboratory. On one night, he suddenly broke into a cold sweat. He felt somebody was watching him with sinister eyes. Suddenly, a gray material form crossed the room and approached Vick. In the vague outline Vick could discern legs, arms and fog where the figure must have a head; there was a dark spot in the center of the fog which might be a mouth. The vision disappeared in the air without leaving a trace.The sound waves made his eyeballs resonate and produced an optical illusion: He saw a figure that didn't exist.*
Soon Vick Tandy managed to discover the factors quite accidentally. Vick's hobby, fencing helped him with it. Some time after the scientist saw the "ghost" he brought his rapier to the laboratory to set it right before a forthcoming fencing tournament. Suddenly Vick felt the blade gripped in a vice started vibrating more and more as if some invisible hand touched it. Vick suddenly arrived at a conclusion that the moving of the blade was resonance oscillations caused with sound waves. He measured the sound in the laboratory and was surprised to see that the sound in the room was incredibly loud; the sound waves were inaudible, but the oscilloscope detected a large amount of noise.. That was infra sound. It took the scientist a lot of time to find out the source of the infra sound; it was emitted by a recently set  ventilator in the air conditioner. As soon as the air conditioner was switched off, the blade stopped vibrating.
The same can be said for the crew of “The Flying Dutchmen”, ships that wandered around the seas without crews on board. The ships were in good repair, but there were no personnel on board. The mystery was unsolved for decades, until it became clear that infra sound was the explanation of the phenomenon. As it turned out, infrasound of seven hertz emitted by ocean waves under some definite conditions was the reason of it. But infra sound of seven hertz is terrible for people: they may go mad and throw themselves overboard.
Further investigation of the phenomenon revealed that sound waves of this low frequency may appear rather frequently under natural conditions.  arises when strong gusts of wind clash with chimneys or towers. These heavy basses penetrate even through very thick walls. Such sound waves start rumbling in tunnel‐shaped corridors.
Everybody knows about ultrasound, right? Sound that's too high-pitched to hear unless you're a dog or a bat.
What is Infra sound? But what about infra sound? There is sound that's too low to hear, and the Earth scientists paying attention to it have things to show us. Human ears can register sound down to about 20 hertz, the deepest bass note. Infrasonics researchers are interested in sounds of 10 Hz and below, all the way down to 0.001 Hz. Lower than that is meteorology! In fact Infra sound, this frequency range is the same one that seismographs use for monitoring earthquakes.
Thats what Infrasound is a sound with a frequency too low to be heard by the human ear. The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath the lowest limits of human hearing (20 hertz) down to 0.001 hertz. This frequency range is utilized by characterized by an ability to cover long distances and get around obstacles with little dissipation.
Infra sound has been known to cause feelings of awe or fear in humans. Since it is not consciously perceived, it can make people feel  vaguely that paranormal events are taking place.The atmosphere itself makes infrasound as bodies of air move over mountain ranges. This is like the sound you make by blowing over your teeth, only about 10,000 times lower in pitch. Tornadoes and turbulence in the upper air produce infra sound. And so might sprites, those mysterious upside-down lightning strikes high above large thunderstorms.  Other infrasound comes from space. Auroras make sounds in the 0.1–0.01 Hz range that can travel 1,000 kilometers. Meteors make infrasonic booms, too, and the listening stations hear them.
Scientific studies (Infrasonic Research): On 31 May 2003, two concerts were staged, back to back, at the Purcell Room London. Each concert featured an hour of contemporary music for piano and electronics, performed by Genia and a new film piece by Ravi Deprees, specially created for the event. At four points during the show, the audience were asked to fill out a page of a questionnaire. This was designed to measure their emotional response to the music and log any unusual experiences (such as shivers down the spine). The questionnaire and psychology experiment were designed by psychologists Ciaran O’Keefe and Professer Richard Wiseman
Just before two of these points, as the audience were absorbed in the film and music, the project team flooded the auditorium with infra sound. The infra sound was produced by a specially made generator and had a frequency of 17Hz.
The two Purcell Room concerts were identical in every aspect, except the use of infrasound. If the generator was on in one piece in the 3pm show, it was off in that piece in the 5pm show (see which pieces had infrasound below). We were careful to use the infrasound at moderate levels so it would be on the cusp of perception. The music masked the infra sound ‐ in theory this meant the audience were never fully aware of its presence. Varying where they put the infra sound enables them to rule out the emotional effects of the other elements of the concert (the music, performance and film). During the concert, infra sound boosted the number of strange experiences reported among the audience, even among those who were unaware of its presence. Unusual reports included a sense of coldness, anxiety and shivers down the spine.
On average, infra sound boosted the number of strange experiences by around 22%. It also increased the intensity of any feelings reported. Many unusual experiences were reported during the concerts, ranging from the emotional (e.g. ‘sense of sorrow’, ‘brief moment of anxiety’, ‘excited’) to the physiological (e.g. ‘increased heart‐rate’, ‘headache’, ‘tingling in neck and shoulders’, ‘nausea’, ‘sense of coldness’). The majority of reported experiences were physiological. These effects are different on each person, attribeted to their own sensitivity of infra sound.
The powerful infrasonic vibrations of jet chassis absolutely saturate the bodies of  Continually saturated with these infrasonic energies throughout their flight time, pilot reflexes are severely diminished. Military procedure recognizes this factor, and routinely limits flight time. It is known that excess infrasonic exposures endanger pilots and their flight missions. Pilot damaging effects include decrements in vision, speech, intelligence, orientation, equilibrium, ability to accurately discern situations, and make reasonable decisions.
The critical importance is the comprehension of human tolerances to infra sound. Military medical teams have long studied the effect of machine vibration on human judgement and behavior out of necessity. If jet pilots and rocket pilots alike evidence even minor errors in judgement through their exposure to infrasound, disaster can result. Certain critical errors in judgement and accuracy have in fact been noted during short flight times.
Infra sound may be produced by wind, by some types of earthquakes, by ocean waves, and by such things as avalanches, volcanoes, and meteors.*Elephants and whales have the ability to emit infrasound that can be detected at a distance of 2 km. Even tigers have been known to emit infra sound, these are just a few.
Which body parts could be and are affected? The Known Symptoms And the Frequency (in Hz)  Abdominal pains 4 - 10 General feeling of discomfort 4 - 9 Influence on breathing 4 - 8 Mis contractions 4 - 9 Chest pains  5 - 7  Lower jaw symptoms  6 - 8  Urge to urinate  10 - 18  Limp in the throat  12 - 16  Head symptoms  13 -20  Influence on speech  13 - 20  Increased muscle tone  13 - 20  Eye resonance  16 - 19  Human auditory range  20hZ - 20kHz
In Conclusion: There is difficulty in recording and reproducing ultra deep tones for study and analysis. They have to be generated on site for experimental purposes. But when performing a paranormal investigation, it is infinitely important to take in the factor of sound as well as EMF for explanation of a paranormal phenomena.
As Always
Be Safe Se Sure
Happy Haunting