Ghosts created by low frequency sounds

Our story begins at a medical manufacturing facility in the midlands of Great Britain. Vic Tandy, an engineer from Coventry University, was doing research in a laboratory at the company. Tandy is an expert in computer-assisted learning (and coincidentally, if I'm not mistaken, I think the "Vic Tandy" might have been an old TRS-80 model they used to sell at Radio Shack). Workers at the lab told Tandy that the building was haunted, but being a reasoning man of science, he didn't believe them. At least, not at first.
Late one night, when Tandy was burning the midnight oil all alone at the laboratory, he had a face-to-face encounter with the unexplained. As he sat at his desk working in the silent, desolate building, a gnawing unease began to overtake him. Although he couldn't put his finger on anything out of the ordinary, something was not right.
"I was sweating but cold and the feeling of depression was noticeable -- but there was also something else. It was as though something was in the room with me," Tandy said. "Then I became aware that I was being watched, and a figure slowly emerged to my left. It was indistinct and on the periphery of my vision, but it moved just as I would expect a person to. It was gray, and made no sound. The hair was standing up on the back of my neck -- I was terrified."
Tandy steeled himself and turned to face the ghostly shape dead-on, but he said it immediately faded and completely disappeared. Concerned that his mind must be playing tricks on him, Tandy packed up and went home. But in the great tradition of haunted house encounters, he didn't flee from the ghost-ridden building and swear never to return -- no sir, he came right back for more. And he got it.
The morning after his weird sighting, Tandy took a break at the lab to spend some time on a hobby of his, namely the sport of fencing. He clamped a fencing foil in a vise so that he could make some adjustments on it, perhaps subconsciously thinking he might need the sword to fight off any unruly ghosts. Tandy briefly left the room, and then returned to see a phenomenal sight. The tip of the foil was vibrating intensely and continuously, for no apparent reason.
The average person might have freaked out and concluded that the poltergeists were trying to go on a foil-whacking spree upside somebody's head. But not Vic Tandy, professional engineer. His first thought was that there might be low frequency sound waves coming from somewhere in the laboratory -- subsonic sounds that can be seen (in the form of surrounding vibrations) but not heard.
One of the perks of being a scientist is that you can usually get ahold of big-time scientific equipment any time you have a crazy hunch about something, and so Tandy was able to test out the laboratory's sound wave properties. His hypothesis was correct: there was a "standing wave" acoustically stuck inside walls of the lab, an infrasound wave vibrating at about 19 cycles per second. The sound waves, which just happened to hit top intensity at a spot right beside Tandy's desk, were being generated by a recently installed extraction fan.
"When the fan's mounting was altered, the ghost left with the standing wave," Tandy said. And that, surely, was the most hum-drum exorcism ever performed in history. But there's a deeper significance to Tandy's discovery than knowing when to tighten some loose bolts. Tandy believes that the low frequency sound also caused his late-night spectral visitation: the cold chills, the sense of paranoia and distress, the hallucinatory figure glimpsed creeping in the shadows. In short, infrasound waves could could be a multi-purpose explanation for most of the commonly reported occurrences in suspected hauntings.
Research has previously proven that exposure to low frequency sound can cause a variety of physiological effects, many of them adverse ones, such as shivering, anxiety and breathlessness. These responses can lead a person to think that some unseen danger is imminent, or feel like he is being watched. Infrasound might even cause hallucinations. Tests at NASA have shown that the human eyeball has a resonant frequency of 18 cycles a second, and will vibrate in sympathy with infrasound waves that have a similar frequency. Under these conditions, there would be a "smearing of vision" that is capable of making someone see evanescent hallucinations in the periphery of their visual field. This effect is reminiscent of the theories of neurologist Michael Persinger, who has suggested that electromagnetic waves can interfere with brain activity and lead people to think they see ghosts or aliens.
To back up his personal observations, Tandy has investigated other sites of reported hauntings, and he claims to have found two more in which infrasound may account for the "presence" of ghosts. One was a building where a wind tunnel in the basement was running during the sighting. Of course, the classical haunted house is an old abandoned mansion without so much as electrical wiring, let alone heavy industrial equipment. But infrasound can still be generated without power -- a standing wave could be caused by wind blowing past a cracked window in a long, narrow corridor, which sounds like a suitably creepy setting. This type of low-frequency sound generation is similar in principle to the deep tooting sound a glass bottle makes when you blow across the top of it.
So it just might be that subsonic sound waves have put the spook in a lot of traditionally spooky places. And what's more, in some cases it may have even been put there on purpose. Archaeologists have discovered that a number of Neolithic tombs in England and Ireland were seemingly constructed so as to make sounds bounce off walls with the intentional effect of being, well, scary. The tombs uniformly create this acoustic environment through the familiar recipe of a long, narrow entryway with an opening to the outside at one end. The ancient architects of these tombs may not have understood infrasound frequencies and Helmholtz resonance, but spookiness was a desirable feature for a tomb, for the purpose of instilling reverence for the dead and discouraging grave-robbers. Through trial and error, they might have struck upon the most sonically foreboding design possible, and stuck with it.
All in all, the Tandy theory of infrasound hauntings is a nifty notion that's tailor-made for Scully to fling at Mulder's next phantom menace. But never fear: the true-believing ghost-hunters of the world will remain undaunted by science's latest whiz in their cornflakes. At the very least, the faithful will knowingly explain that real ghosts produce subsonic sounds, thereby hijacking all the salient facts over to their side of the argument. Or they could just pretend that this whole discovery resonates at an ultra low frequency, and never hear a word of it.