Man-made structures, such as engines, cars, buses, trains, motorcycles, and airplanes also produce infrasound. John Cody also noted that pilots exposed to infrasonic vibrations of jet chassis experience a reduction in "vision, speech, intelligence, orientation, equilibrium, ability to accurately discern situations, and make reasonable decisions."
Infrasonic vibrations, though harmful, can be pleasantly stimulating in mild levels. The effects of brief, mild exposure can give a feeling of invigoration for hours. While a person may FEEL invigorated and euphoric, his body is being subjected to an elevated heart rate, elevated blood pressure, a release of endorphins, and the "fight or flight" adrenaline response. Feeling the effects of high-intensity/low-frequency sound can actually become an addiction, partially due to the release of endorphins in the body.
Depending on the pitch, infrasound can cause physical pressure, fear, disorientation, negative physical and mental symptoms, explode matter, incapacitate, and kill. For example, in World War II, Nazi propaganda engineers used infrasound to stir up anger in the large crowds that had gathered to hear Hitler. The result was a nation filled with anger and hatred.
Studies show the different ways in which infrasound affects the human body. As infrasound pitches, or cycles per second, decrease, deadly effects on the body increase. Infrasound disrupts the normal functioning of the middle and inner ear, leading to nausea, imbalance, impaired equilibrium, immobilization, and disorientation. Exposure to even mild doses of infrasound can lead to illness. Increased intensities of infrasound can result in death.
