18.98 Hz — often rounded to 19 Hz — is known as the "Ghost Frequency" or "Ghost Tone." It is an ultra-low frequency that has been linked to reports of paranormal-like experiences: shadowy figures in peripheral vision, feelings of presence, unexplained chills, and a pervasive sense of being watched. The theory connecting this frequency to ghost sightings was first proposed by engineer Vic Tandy in 1998.

Tandy was working in a laboratory where staff had reported feeling uneasy, seeing grey apparitions, and experiencing cold chills. He discovered that a newly installed extraction fan was producing a standing wave at approximately 18.98 Hz throughout the workspace. When the fan was modified, the ghostly experiences stopped. Tandy subsequently found similar infrasonic conditions in a reputedly haunted medieval cellar in Coventry.

The connection to ghost sightings may lie in the frequency's proximity to the resonant frequency of the human eyeball (approximately 19 Hz), which could cause subtle visual disturbances interpreted as apparitions. Delivered here as a binaural beat with a 210 Hz carrier (left: 200.51 Hz, right: 219.49 Hz). At safe listening volumes, it's an intriguing curiosity — not a ghost machine.