Passage Graves Read Free

his backpack and tapped it lightly. “What do you hear?”
    Scott smiled. “A drum.”
    Carefully studying the walls, David moved near Scott’s left shoulder. “How about now?”
    After a moment, Scott opened his eyes, blinking in disbelief that David was still drumming. “I can’t hear it!” he exclaimed.
    David moved again, this time to the right, maintaining the rhythm as he eyed the walls and stopped at a precise area within the chamber. “What about now?”
    Scott grabbed his ears . “It hurts.”
    “That’s low frequency sound propagating off the walls,” David spoke over the distortion . He nodded for the class to look at the acoustic monitors. The stylus arrow fluctuated around 120 dB and the frequency counter’s digital display read 10 Hz. A few students held their stomachs, sensing the vibrations.
    “The human ear can dete ct sounds between 20 and 16,000 Hz. What you’re feeling is subsonic noise, the interaction of sound waves from the drum and the drum’s noise reflecting off the walls. In some places, equal proportions of sound collide and create standing waves or nodes—that means you won’t hear the drum at all. In other places, resonances detach from their source and move around the chamber. The drum noise can seem like it is coming from really far away or like it’s originating inside your head. That’s amplified resonance. These are antinodes or sweet spots. Believe it or not, this drum can also be heard inside Camster Long, another passage grave 650 feet away from us, even though it can’t be heard in the open air between the two cairns.”
    David smiled. For once, his students were listening. He stopped drumming. “This is science! Acoustic architecture!”
    Scott lowered to his knees, still holding his stomach.
    “There is nothing supernatural about these ruins,” David said. “No mysticism. No space travel. Definitely no aliens.” He laughed. “Think about it. You’re at some ceremony centuries ago, inside a dark chamber with a rhythmic, pulsing beat. Put all these things together.”
    Sixteen blank stares. At least they were interested blank stares.
    “Come on,” he said. “You just witnessed how powerful sound can be. Add fifty more people and purple mushrooms.”
    “Brilliant!” the student with a nose ring shouted.
    David nodded at him. “Science just shed light on the dirty habits of a few prehistoric potheads.”
    The class erupted with applause. A few of students would leave the University of Aberdeen with an appreciation for science, even if it was based on prehistoric rock’n’roll and hallucinogens.
    Scott let out an agonizing moan. A trickle of blood fell from his nose.
    David set down the drum.
    One of the girls offered tissue from her purse, and David pressed it against Scott’s nose. “Sorry Scott. Give it some pressure,” he said.
    Scott hunched sideways and vomited o n David’s shoes.
    Everyone backed away in disgust.
    David kept one hand against Scott’s nose and waved to the student with the nose ring. “Take him outside, okay? Fresh air should help.” He handed Scott the tissue and patted him on the shoulder. “Sorry, man.”
    The s tudent led Scott down the tunnel.
    David kicked vomit off his boots. He looked up at the class, surprised to see they were intently interested. Their boring American teacher was suddenly cool. A modern Indiana Jones.
    “Professor Hyden, look.” A girl pointed at the frequency counter.
    The digital readout fluctuated between 5 and 10 Hz but everyone was quiet.
    David tapped the plastic co ver. The counter continued to rise and fall.
    “Must be broken, ” he said. He unplugged the machine from its power source. The readout faded then disappeared.
    Some of the students tittered nervously.
    “Let’s call it a day,” David said shoving equipment into his backpack. “I’ll see everyone next Thursday at the University.” He zipped up the bag, keeping out the broken frequency counter. “Hey!” he yelled