Low-frequency sound waves at 18.98 Hz can vibrate your eyeballs, creating ghostly visual illusions and a haunting sense of presence.

The phenomenon of infrasound affecting human perception was famously documented by engineer Vic Tandy in the 1980s. While working in a medical equipment laboratory, Tandy and his colleagues reported feeling a sense of dread and seeing gray, flickering apparitions. After investigating, Tandy discovered a silent extractor fan was emitting a frequency of 18.98 Hz—nearly identical to the resonant frequency of the human eye.The human eye is a fluid-filled sphere with a specific frequency at which it vibrates most intensely. When exposed to 18.98 Hz, the eyeball begins to resonate, causing the vitreous humor to vibrate and distort the image on the retina. This distortion typically manifests as dark or gray blobs in the peripheral vision, where the eye is most sensitive to movement.Beyond visual illusions, infrasound affects the inner ear and chest cavity. Research by Dr. Richard Wiseman and colleagues has shown that these low frequencies can trigger hyperventilation, chills, and localized pressure in the ears. The brain often interprets these physical sensations as a "fight or flight" response, creating the feeling of being watched by an unseen entity.Infrasound is common in the natural and modern world, generated by wind hitting buildings, old plumbing, and industrial fans. A 2003 experiment with 750 people at a concert hall in London found that adding infrasound to music significantly increased reports of anxiety and sadness. This evidence suggests that many legendary haunted locations are simply areas with elevated levels of low-frequency noise.