In this episode, we discuss the mysteries of infrasound and what are the possible effects made by these strange sound waves. You can listen along with our episode here.
What is infrasound?
According to an article from Science Direct, the definition of infrasound and low-frequency noise, in its popular definition is sound below a frequency of 20 Hz which is clearly audible. The hearing threshold having been measured down to 0.001 Hz.  The true range of infrasound starts to leave the human hearing range around 16 Hz. “Sources of infrasound are in the range from very low-frequency atmospheric fluctuations up into the lower audio frequencies. These sources include natural occurrences, industrial installations, low-speed machinery, etc. Investigations of complaints of low-frequency noise often fail to measure any significant noise. This has led some complainants to conjecture that their perception arises from non-acoustic sources, such as electromagnetic radiation.
Over the past 40 years, infrasound and low-frequency noise have attracted a great deal of adverse publicity on their effects on health, based mainly on media exaggerations and misunderstandings. A result of this has been that the public takes a one-dimensional view of infrasound, concerned only by its presence, whilst ignoring its low levels.” 
History of Infrasound
French scientist Vladimir Gavreau was interested in infrasonic waves when it first came about in his laboratory during the 1960s when he and his laboratory assistants experienced shaking laboratory equipment and pain in the eardrums, but his microphones did not detect audible sound. He concluded it was infrasound caused by a large fan and duct system. 
According to Vice, Hitler’s chief architect, Albert Speer set up research to explore using sonic warfare to create a tool of death. He created an acoustic cannon to create explosions of methane and oxygen. 
This device could send out a focused beam of sound that was magnified by huge parabolic reflector dishes. The idea behind this device was that sound that was repeatedly sent out could compress and release particular organs in the human body and potentially kill someone standing within a 100-yeard radius in about 30 seconds 
The infrasonic sound sometimes results naturally from severe weather, such as surf, lee waves, avalanches, earthquakes, volcanos, waterfalls, calving icebergs, meteors, lightning, and upper-atmospheric lightning.  Nonlinear ocean wave interactions in ocean storms produce pervasive infrasound vibrations around 0.2 Hz, known as microbaroms. According to the Infrasonics Program at NOAA, infrasonic arrays can be used to locate avalanches in the Rocky Mountains. 
Whales, elephants, hippopotamuses, rhinoceroses, giraffes, okapis, peacocks, and alligators are known to use infrasound to communicate over distances—up to hundreds of miles in the case of whales.  Some animals have been thought to perceive the infrasonic waves going through the earth, caused by natural disasters, and to use these as an early warning. An example of this is the 2004 Indian Ocean earthquake and tsunami. Animals were reported to have fled the area hours before the actual tsunami hit the shores of Asia. 
Human Created Sources
Infrasound can be generated by human processes such as sonic booms and explosions (both chemical and nuclear), or by machineries such as diesel engines and specially designed mechanical transducers (industrial vibration tables). Certain specialized loudspeaker designs are also able to reproduce extremely low frequencies 
Below 10 Hz it is possible to perceive the single cycles of the sound, along with a sensation of pressure at the eardrums. One study has suggested that infrasound may cause feelings of awe or fear in humans, making people feel that odd or supernatural events are taking place. There is growing evidence that infrasound may affect some people's nervous system by stimulating the vestibular system. This is an effect that is often seen with seasickness. Infrasound can also cause effects of annoyance, fatigue, pressure in the ear or tinnitus (ringing in the ears), dizziness, and sleep disturbances.
Infrasound is one hypothesized cause of death for the nine Russian hikers who were found dead at Dyatlov Pass (near Siberia) in 1959.
Infrasound and the Paranormal
It turns out there might be an explanation for hauntings, infrasound. These low-frequency vibrations caused blurred vision, dizziness, and feelings of fear in humans.
This can rule out some hauntings but not all. We have heard Greg Newkirk, from Hellier mention this in some of the live streams and investigations they have done. Infrasound is also mentioned in the book Men Who Stare at Goats by Jon Ronson.
The worldwide phenomenon known as "The Hum" has been reported in various locations around the world, ranging from vibrations to a hum to similar to a low bass hum or the hum of a diesel engine.  Some associated places with this are Taos, New Mexico with the Taos Hum, Windsor, Canada with the Windsor Hum, and Hythe, Hampshire, UK are just a few. Many of these are believed to be linked to infrasound in some ways.
Infrasound is not all bad
While infrasound does have its bad points it also has some good ones. One of the ways infrasound is good is through the Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission. They use infrasound as one of the monitoring technologies, along with seismic, hydroacoustic, and atmospheric radionuclide or radioactive isotope monitoring. Infrasound is now being used alongside radar to detect tornados. This partnership allows there to be more time to send out a warning to get people to safety.