Have you ever had a feeling, a sense of foreboding that you just couldn’t shake? If you have, you aren’t alone, and the sensation you are experiencing may be explained by the phenomenon of infrasound.
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A case of this nature is described by Vic Tandy’s Ghost in the Machine paper where he discusses the paranormal activity in a medical lab he was working at. His colleagues had noted “a feeling of depression” in the building they were working in, leading them to believe it was haunted. Tandy initially put this down to the wheeze of the life-support machines. This came to a peak when he saw an ominous grey figure in his peripheral vision, which disappeared when he looked directly at it.
The breakthrough came when Tandy, a fan of fencing, brought his sword to the lab and noticed the sword’s foil strip vibrating. This phenomenon led him to investigate the source of the vibration, where he discovered that a newly installed ceiling fan was creating a standing wave of infrasound in the lab. Interestingly, this wave resonates with the eye, causing objects such as dust in your peripheral vision to appear larger. This is what caused Tandy to see a figure.
Tandy found that the frequency of resonance was around 19Hz, which is just below the threshold of human hearing (at around 20Hz). Following this, he carried out an investigation into a haunted pub cellar near Coventry. People had reported seeing a ghostly grey lady. An infrasound frequency of 19Hz was also found at this location.
Interestingly, infrasound is also used in the animal kingdom and research now shows that a tiger’s roar prior to an attack contains frequencies in the infrasound range. The researchers also found that this is how tigers and other animals communicate as infrasound can travel much further than higher frequency sound over distance.
Fairly little is known about infrasound but researchers in New Mexico have been investigating using controlled missile explosions. Full details of the experiment can be found here.
The short version of this is that an Orion missile had been loaded with a 50lb explosive and set to detonate at the White Sands Missile Range. The missile was set to be launched and detonated 30 miles above the desert floor, triggering powerful infrasound waves that would travel across the southwestern US. While the sound waves above 20Hz only travelled a few miles at most before fading, infrasound has the capability to travel much further, even across oceans. 20 microphone arrays were set up in six different states to record the subsequent infrasound waves.
It’s not immediately apparent how investigating infrasound in this way is particularly useful but it can have many related uses. Take for example the issue of nuclear testing by nations such as North Korea. Where nations are (supposedly) on the verge of pressing the big red nuclear button, an event such as a stray asteroid could cause tensions to boil over. By using infrasound and triangulating the source, the true cause of vibrations like a nuclear explosion or asteroid impact can be determined and catastrophe averted.
Aside from Mutually Assured Destruction, natural disasters can also be predicted using infrasound. As infrasound travels much faster than normal sound, the inaudible first vibrations of earthquakes and volcanic eruptions can now be recorded. The relevant emergency services can then be warned, potentially saving lives. It is also thought that infrasound may be used to predict the path of future hurricanes although this application needs further research.
Infrasound isn’t all scary sounds and disaster precautions though. A man called Tim Storms actually has a vocal range that extends into the infrasound range. Tim is the Guinness World Record holder of the lowest human voice and the widest vocal range for a male. Imagine being able to convince people around you that there’s a spirit haunting them if you wanted… although who would be that cruel?