Spooky Sounds

Imagine, you're sitting alone one hot summer night, enjoying a nice book underneath your ceiling fan. The cool breeze is initially calming, but then you start to feel uneasy. You look up, distracted from your book, but find nothing out of the ordinary, so you shake it off and go back to reading. A few minutes later, you still feel like someone is watching you, and, afraid to move and look up from your novel, you realize there is a gray blob standing at the edge of your vision. Watching you. You finally jerk your head up to see who's there, but the figure has disappeared.

Obviously, your house is haunted.

Photo: From VisitFindley.com

...or maybe not. I briefly talked about infrasound before here, and it turns out that it is likely also the cause of psychological effects which are commonly attributed to ghosts. You can read all about it in this paper by Vic Tandy and Tony R. Lawrence, published in the Journal of the Society for Psychical Research, but infrasound is basically sound waves just below what humans can hear, about 20hz.

First, let's talk about that 'creepy' feeling that you got while you were reading, like someone is behind you or watching you. Many objects vibrate at these low frequencies, such as your ceiling fan from the intro story, and, because people can't consciously sense it, they tend to feel that something supernatural is at work.

Next, seeing shapes out of the corners of your eyes. In the paper, Vic Tandy recounts working in a supposedly haunted lab, where he discovered that the extractor fan was vibrating at about 19Hz, very close to what NASA sites as the resonant frequency of the eye. Basically, the low sound waves vibrate your eyes, making you see shapes that aren't there.

So this Halloween, if you feel like making your friend think their house is haunted, try using their computer to go to this website, turn their speakers full blast, and leave their computer on.

Photo: A Place to be Happy