INFRASOUNDS

Infrasound is low frequency sounds, covering from the lower limit of human hearing, about 16 or 17 Hz, down to 0.001 Hz. Infrasound is characterized by the ability to cover long distances and get around obstacles with little dissipation. Earthquakes shake the air along the ground, creating seismic infrasound, that can travel far from the epicenter. Volcanoes make some impressive infrasound. Big sea storms generate air waves, called microbaroms, from the water waves beneath. Probably the first observation of naturally-occurring infrasound has been in the Krakatoa eruption in 1883, when concussive acoustic waves circled the globe seven times or more and were recorded on barometers worldwide. Infrasound sometimes results naturally from ocean waves, avalanches, earthquakes, volcanoes, and meteors. Infrasound can also be generated by man-made processes such as explosions, both chemical and nuclear.