What frequency range is defined as infrasound?

Infrasound refers to sound waves that are below the threshold of human hearing, specifically those frequencies that are lower than 20 Hz. This means that any sound produced in this frequency range is inaudible to most humans, who typically can hear sounds from 20 Hz up to approximately 20 kHz. Infrasound is often generated by natural phenomena such as earthquakes, volcanic eruptions, and even by man-made sources like machinery or large vehicles. Understanding this concept is important in fields related to acoustics, environmental science, and even hearing aid technology, as it highlights the limitations of human hearing and the diverse range of frequencies that exist in the environment.