When it comes to the supernatural, you can place me in the “firmly skeptical” pile. I’m the sort that believes that there is always an explanation for the inexplicable. Assigning credit/blame to something supernatural is ridiculously primitive. Science will set you free.
Take the case of the uneasy feelings we sometimes blame on ghosts and hauntings and poltergeists. It could be that we’re just feeling sounds that we can’t hear.
There are many possible explanations for hauntings, not least that humans are highly suggestible creatures, especially when we want to believe. But some ghost sightings might actually be the result of sounds — sound waves that vibrate just below our range of hearing, dubbed the “fear frequency.”
Sound is basically mechanical energy in the form of a pressure wave with crests and troughs: vibrations create a disturbance in the surrounding air and ripple outward, like tossing a pebble in a pond. Frequency measures how many crests occur within one second in a wave. The unit of measurement is called a Hertz (Hz), and 1 Hz is equivalent to 1 vibration per second. A plucked guitar string might vibrate 500 times per second, causing surrounding air particles to vibrate at the same frequency, so the sound wave’s frequency would be 500 Hertz.
The typical range for human hearing runs from 20 Hz to 20,000 Hz (20 kHz), although this varies from person to person, and shrinks as we age. Under ideal lab conditions, some people can pick up sounds as low as 12 Hz — well into the “infrasound” range. But even when we don’t consciously hear such sounds, they may induce feelings of anxiety, especially at higher intensities. This has led some people to dub infrasound in the 18.9 Hz range — i.e., just a tad below the threshold for human hearing — the “fear frequency.”
Read on at Gizmodo. Meanwhile, fear the “brown note.“