In 1998, researcher Vic Tandy discovered that a frequency of approximately 18.98 Hz — just below the threshold of human hearing — was responsible for reports of ghostly apparitions in his laboratory. The frequency, produced by a faulty ventilation fan, resonates with the human eyeball at its natural frequency. This causes the vitreous humor to vibrate, producing visual disturbances in peripheral vision — smeared shapes, shadow movements, the sensation of a presence. The effect has been independently verified in haunted locations worldwide. Churches, castles, underground tunnels — many sites famous for ghost sightings contain environmental sources of infrasound near 19 Hz. Fragment Zero investigations have documented this frequency appearing in digital contexts where it should not exist: embedded in streaming audio, modulated into notification sounds, present in the background noise of specific video calls. The frequency 19.47 Hz is of particular interest. It corresponds to the tetrahedral constant — the latitude (19.47 degrees) at which a tetrahedron inscribed in a sphere contacts the surface. This value appears in the energy upwelling patterns of every gas giant in our solar system. Whether this is coincidence or design remains an open investigation. See: CLASSIFIED FILE 19, FILE 7F3A