Engineering designer Vic Tandy had just seen a ghost. That, or he was losing his mind, he thought.
|Image Credit: Mark Strozler, Creative Commons by-nc-nd|
It happened the way these things often do; he was alone in the laboratory, after dark. It was a long, low building, standing on a lot which it shared with a population of stray cats that lived somewhere nearby. But this, the feeling of being watched that suddenly overtook him at his desk…this wasn’t a cat.
In the previous weeks, the lab had become rife with rumors of a haunting. His coworkers had told him of strange chills, and feelings of depression that would sweep over them and then depart just as rapidly as they had come. It was strange, to be sure, to have so many avowed skeptics reporting the same phenomena, but Vic initially chalked it up to the power of superstition and suggestion.
It only started to become truly troubling when Vic watched a coworker turn to address him, assuming that Vic was standing right over his shoulder, when in reality he was on the far side of the lab. His colleague had felt another person’s presence there; he was sure of it. Before that, a cleaning woman fled the building one morning just as Vic arrived, swearing that she had seen something in the room with her, which had promptly vanished as soon as it was noticed.
So when Vic was working late one night, writing at his desk, and began to feel as though he wasn’t alone, his hair stood on end. An unpleasant cold feeling overtook him, and the certainty that he was imagining things was gone from his body, leaving in its place nothing but doubt and terror. He got up, his mind grasping at straws to explain rationally what was happening to him. There were canisters of various gases around the room, and he checked each of them in hopes that this wave of dread could be banished with the closing of a valve.
Vic grabbed a cup of coffee and sat back down at his desk, in spite of his unease. He had just resumed writing when, out of the corner of his eye, he saw something. He sat frozen with apprehension, desperately curious for a look at it, but too scared to move. As the less rational parts of his mind howled at him to run and prayed fervently for deliverance, a grey shape started to take form at the edge of his vision. It was silent and featureless, as far as he could tell, but seemed to have a distinctly human character to the way it moved. Mustering his courage, he silenced his primal instincts (which had by this point doubtless moved from howling to gibbering) and turned to look the specter in the eye.
It faded into nothingness, taking with it most of the physical discomfort it had brought. Vic went home, thinking to himself that he ought to see a psychiatrist, and our story might end here if Vic hadn’t had the unusual luck of being a sporting man as well as a scientist. He made a pastime of fencing, and had a tournament to enter in the near future.
Where less willful people might have taken a mental health day, Vic returned to the lab the next morning, emboldened by the light of the sun. He brought his fencing sword with him, so that he could use the bench vice at the lab to hold the blade while he attached a thread for the handle. After securing the blade in the vice, he left for a moment to get some oil. When he returned, he was alarmed to see the free end of the sword wagging up and down; he was still the only one in the lab, and it had been perfectly still when he left.
His alarm soon turned to delight as he realized that he may have just caught the demon which had been plaguing him and his coworkers for months, and with a sword, no less. Fixing the blade onto a smaller, more mobile vice, he tested his hypothesis by dragging the apparatus along the floor from one end of the lab to the other. Its oscillations grew wilder and wilder until he passed his desk, where they started to diminish. By the time he reached the far wall, the blade was totally still again.
Suddenly, his experience from the night before started to make sense; he’d been working with his head stuck smack in the middle of a high-pressure node! When he turned his head to face his fear, he had moved out of the worst of it, and the effect abated. The haunting began, he later discovered, when a new fan was installed in the air handling system at one end of the lab; several times a second, a wave of air pressure would sweep through the room and reflect off the back wall, colliding with the next wave of air pressure at the room’s center. The new fan had been powering a standing wave of infrasound, which peaked in intensity at the center of the room, right by Vic’s desk.
Having found only the one high-pressure node, Vic concluded that the laboratory was half as long as the infrasound’s wavelength. Knowing the speed of sound to be roughly 343 meters per second, and that the lab was about 30 feet (9.1 meters) long, he calculated sound’s frequency to be: