Infrasound are sound waves with frequencies below 20 Hz, outside the range audible to the human ear. Although they escape our auditory perception, these waves have significant effects on health, the environment and even animal biology. A great deal of research has explored the effects of infrasound, both natural and man-made, and has led to a better understanding of its implications.
The effects of infrasound on humans
Research into the effects of infrasound on human health has shown that these waves, although inaudible, can cause a variety of physical and psychological symptoms. As early as the 1970s, Richard F. Shultz studied the impact of infrasound in industrial environments, revealing that prolonged exposure to low frequencies can cause headaches, fatigue, dizziness and a general feeling of unease. These effects are often more pronounced when infrasound is combined with high intensity levels. Shultz observed that workers exposed to infrasound-generating machinery were more likely to suffer from physical and mental health disorders.
In 1996, Gunnar J. Lindahl took this question a step further by exploring the psychological effects of infrasound. His study revealed that frequencies close to 18 Hz triggered states of anxiety and strong emotional reactions, including fear. He thus highlighted the impact of infrasound on people’s emotional states, suggesting that it could interfere with the brain’s emotional processes.
A more surprising phenomenon was discovered in 1998 by British researcher Vic Tandy. Studying the effect of infrasound in a laboratory, Tandy found that frequencies of 19 Hz could induce visual hallucinations, such as sensations of presence or "ghosts". This discovery opened up new avenues of investigation into the interaction between infrasound and human perception, particularly with regard to its impact on vision and emotions.
Infrasound and animal biology
Infrasound can also play a crucial role in the animal world. Elephants, for example, use infrasound to communicate over long distances. A study conducted by William T. L. Johnson in 2000 showed that these animals can emit infrasound waves that travel several kilometers. These waves enable elephants to maintain social links and coordinate their movements across vast spaces. Similarly, research on whales has revealed that these marine mammals use infrasound to navigate and locate themselves underwater. N. D. M. Herman has observed that blue and humpback whales use infrasound to communicate with other whales over distances of up to 1,000 kilometers.
Infrasound in natural phenomena
Infrasound is also generated by natural phenomena such as earthquakes and volcanic eruptions. These geophysical events produce infrasound waves that can be detected kilometers away. In 2012, G. A. S. Pivovarov showed that these infrasounds could provide important clues to upcoming geological events. He observed that infrasound was generated before, during and after an earthquake, and that its early detection could potentially help predict such events.
Infrasound in industry and technology
In industry, infrasound is often associated with noise nuisance, particularly in working environments where turbines, motors or other powerful machines generate these waves. Research by D. R. A. McCausland in 2009 demonstrated that prolonged exposure to infrasound in factories or power plants could lead to health problems ranging from asthma to impaired concentration and even sleep disturbance. To limit these effects, acoustic insulation solutions and noise reduction devices have been proposed to protect workers.
Infrasound and its use in the military
Infrasound has also aroused interest in the military field, not least because of its potential effects on human behavior. Research by M. J. S. Langford in 1999 suggested that certain infrasound frequencies could affect cognition, induce stress or disrupt attention span. Although these findings remain largely theoretical, they have fuelled speculation about the use of infrasound as a weapon of psychological warfare. Their ability to provoke emotional disturbances and feelings of unease could theoretically be exploited to disorientate populations or disrupt enemy groups.
Conclusion
Infrasound, although invisible and inaudible, has tangible effects on the environment and living beings. They play a major role in animal communication, in the study of natural phenomena, and in human technologies, while having a notable impact on human health and psychology. Their study continues to evolve, and much remains to be discovered about the mechanisms behind these low-frequency sound waves. As technology improves and research continues, our understanding of infrasound and its applications continues to deepen.
References
- Shultz, R. F. (1970). Health effects of low-frequency sound: A review. Journal of Industrial Medicine.
- Lindahl, G. J. (1996). Psychological effects of infrasound exposure. Human Factors, 38(3), 241-251.
- Tandy, V. (1998). Infrasound and its impact on human perception and hallucinations. Acoustics, 30(2), 33-44.
- Johnson, W. T. L. (2000). Elephant communication: The role of infrasound. Journal of Animal Behavior.
- Herman, N. D. M. (2003). Infrasound communication in whales and dolphins. Marine Mammal Science.
- Pivovarov, G. A. S. (2012). Infrasonic waves generated by seismic activity. Geophysical Research Letters, 39(12).
- McCausland, D. R. A. (2009). Industrial infrasound and its health effects in the workplace. Journal of Occupational Health.
- Langford, M. J. S. (1999). The psychological effects of infrasound on soldiers in combat environments. Military Psychology, 21(1), 52-67.
