Infrasound Blues?

Ever wonder why you can enter a room, and suddenly feel a sense of dread, or fear? Well, most people have chalked it up to places being haunted! Indeed, it’s an easy conclusion to come to when you feel uneasy in a room, and even see blurry images around the room. Often, in many places, different people, without prior knowledge of each other and their situations, can feel or see things in the same place. So it must be haunted, right? WRONG! Science to the rescue!

Assuming you haven’t been awake for 4 days straight (because that can cause these things too), the culprit is very likely to be something called infrasound! Infrasound is sound just below the human range of hearing, which is roughly around 18Hz in frequency (cycles per second). Despite human’s inability to hear infrasound, our ears (or even body via vibrations!) can detect them, and studies have shown that we often feel dread or fear when we pick up the sounds. This easily sets the stage for horror movies and haunted houses, but does it really go deeper than that?

Indeed, infrasound, if at the right frequency, can actually resonate with our eyeballs. When something resonates to a certain frequency, we mean it is subject to vibrate when subjected to sound waves of that frequency. Tuning forks have specific pitches because when we make them vibrate, it will have a specific frequency that corresponds to a pitch’s given frequency. If our eyeballs pick up the infrasound’s frequency that it resonates at, it will vibrate and can cause us to see images of figures that aren’t actually there. Indeed, if you wear glasses with slight dust specks on them, the vibrations can cause the eye to register the static flake as being a moving blur. Infrasound can make you experience pain, and perhaps even bleeding!

Don’t get me wrong though, infrasound isn’t just a bad thing. In fact, there may be an evolutionary reason as to why we feel these things when our ears detect infrasonic waves. Some of the natural phenomena that produce infrasonic waves are volcano eruptions, earthquakes, and avalanches, just to name a few. This could give us a subconscious way of knowing that danger is near! It is believed that many animals use infrasound to detect such disasters to give them ample time to adapt or run. They can do this because infrasound can travel over very long distances without encountering too much interference. In fact, elephants can produce infrasonic waves through the ground using their feet to communicate over distances of 2 kilometers!

In addition to natural sources, many man-made sources can create infrasound. This can cause vibrations in many objects, another sign of “hauntings” in your surroundings. In fact, we sometimes use it in music or movies to give people that feeling of unease. According to wikipedia, Paranormal Activity used infrasound in its soundtrack—I can believe it, a LOT of my friends were really scared by that movie, even the ones with strong resolve. Infrasound being produced by man-made devices such as fans and infrasonic whistles have been shown to be the cause of places being haunted, and since their removal, the place became “normal.”

So there you have it! Now you know a really good way to scare the living daylights out of your friends when you make your own haunted houses. Too bad we’re now in November and you just missed Halloween…maybe next year!