Have you ever wondered what sounds publishes a ghost? Perhaps the engineer Vic Tandy is already known. In the early 80's Tandy worked in the laboratory on the development of medical devices. The staff of rumors began to circulate that the laboratory is haunted. Tandy attributed this constant wheezing sound of the building work in the life support system.
One evening, when Vic was working alone in the lab, he began to feel distinctly uncomfortable feeling, his body cold sweat, and the hair on his neck stood on end. He was sure that he was being watched. Then, the corner of his eye, Tandy said an ominous gray shape slowly across the field of view. When Tandy turned to stand up to face him, the silhouette disappeared. Vick was horrified and went straight home.
Tandy was a keen fencer, and the next day he noticed that hamstrung rapier blade rapidly vibrate up and down. He found out that the cause of vibration was a constant sound wave oscillates between the end walls of the laboratory, and peak intensity in the center of the room. Calculations carried out by them, have shown that the incidence of permanent wave was about 19 hertz (cycles per second). He soon discovered that the source of this wave is the newly installed extractor fan. Once the fan was turned off, the sound wave disappeared.
The key here is the frequency: The frequency at 19 Hz in the range known as infrasound. At the same time, the range of frequencies that the human ear can perceive, begins with a 20 hertz. Tandy found that low frequencies in this range can have a different impact on people and animals — with the consequences in the form of discomfort, dizziness, blurred vision (for eyeballs vibrate themselves), pulmonary oxygen saturation, and fear, until the attacks of acute anxiety state with panic attacks.
A more recent study was conducted in a supposedly haunted pub from the 14th century, located in Coventry. For years, people have reported the terrible events that happened to them there to experience, including in the form of a ghostly vision gray lady. Here Tandy also found a permanent wave with a frequency of 19 Hz, which allowed him to significantly bolster his theory by evidence.
As an interesting analogy, the researchers found that the roar of the tiger to attack contains frequencies with a range of about 18 Hz, which can be confusing and paralyzing the intended victim. Maybe it sounds so afraid?