# An engineer traced a haunting to 19 Hz > In 1998 a Coventry University engineer traced a haunted lab to a fan producing sound too low to hear but close enough to his eyes' own resonance to shake his sight. August 20, 2026 · https://justog.club/stories/the-frequency-you-cant-hear One sine wave, drawn slow and wide, filling the chest edge to edge. Only two and a half cycles fit across the whole print. Above it, small: `19 Hz`. Below, fainter, a bracket marking the range of human hearing — starting well to the right of the wave. ## Why does the wave sit outside the hearing bracket? Because 19 Hz is below what a human ear registers as sound at all, and the bracket is there to prove it. The wave on this print isn't decorative — it's drawn at the actual frequency the print is about, and the bracket beneath it marks where hearing starts. The wave sits to the left of it the whole time. You're looking at a sound. You were never going to hear it. ## Where does 19 Hz actually come from? From a documented case: in 1998, an engineer at Coventry University was working late in a lab with a reputation for being haunted. He felt dread, a cold sweat, and saw a grey shape at the edge of his vision. He traced it to a newly installed extractor fan producing infrasound at about 19 Hz, and published the finding as "The Ghost in the Machine" in the Journal of the Society for Psychical Research. That's his account of that one case, not a claim that every reported haunting has a fan behind it. ## Why did a fan make him see a shape? Because the human eyeball has a resonant frequency of its own, sitting almost exactly where the fan did. The eyeball's resonance sits around 18–19 Hz. Sound at that frequency doesn't pass through the body unfelt; it can shake the eye itself, smearing whatever sits at the edge of vision. The shape he saw vanished the moment he looked straight at it, which fits a mechanical vibration far better than it fits a figure standing in the room — [the same blind spot that empties your night vision the instant you look right at something](/stories/movement-in-the-corner-of-your-eye) is doing different work here, but the same lesson: what registers at the edge and what registers head-on aren't answering the same question. ## Who owns a frequency, or an account of feeling dread in a lab? Nobody. A physical measurement and a documented case aren't property to license. 19 Hz is a measurement, not an invented mark, and the published account is a matter of record, not a creative work this print copies. Nothing here reproduces the paper, the name attached to it, or a likeness — the print states a number and draws a wave, which is the extent of what's borrowed. ## Does this explain every reported haunting? No — it explains one case, the one that was investigated and written up by the person who lived it. The print isn't arguing that infrasound sits behind every cold room or grey shape anyone has ever reported. It states what happened in that lab, at that frequency, to that one person's eyes. A mechanism that accounts for a single case convincingly says more than a claim that tries to cover every case, because the first one is actually true. ## Doesn't naming the cause make the dread go away? Not for the person standing in the room at the time — the explanation only arrives afterwards. The dread and the shape came before any idea that a fan was involved. Knowing the mechanism now doesn't undo what a body does when it's exposed to a sound it can't hear; a print of the wave is closer to a diagram of what happened than to a reassurance that nothing did. ## Does it print well? Yes, as a single hard line rather than a filled or shaded curve. A sine wave loses its point the moment it's rendered soft — the reader needs to trace it as a clean, continuous stroke against a plain ground, the way [a rhythm written as dots rather than a stave still reads as timing](/stories/the-knock-pattern) without extra ornament. Charcoal or black grounds with the wave in a single pale ink, the numerals kept small and plain, keep the whole thing reading as a measurement rather than an illustration — closer to [the flat, factual look analog horror already leans on](/stories/analog-horror-aesthetic) than to a drawing of a ghost. ## How do I get one made? Describe the frequency at [JustOG](/) — the number, how many cycles fit, what sits beneath it. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to order and shipped. Designs other people have published are in the [shop](/shop). The fan is still running. You just can't hear it from here.