You probably already know that the normal lower limit of adult human hearing is 20 Hz (Hertz) or cycles per second. Enter Infrasounds: low-frequency sounds, lower than the normal limit of human hearing, which have a very long wave that goes between particles and molecules rather than bouncing off of them. High-intensity infrasounds extend in the megahertz range and well beyond but their frequency level is below 20 Hz so you can feel but not hear them. Sometimes you can hear part of the sound and feel the rest. Sometimes you can only feel the sound. Infrasound can be generated by sonic booms, explosions (both chemical and nuclear), machinery such as diesel engines, trains, planes flying overhead, large-scale subwoofer loudspeakers (e.g., rotary woofers), wind turbines, specially designed mechanical transducers such as industrial vibration tables, and very low pedal pipes on a huge pipe organ. Infrasounds can result naturally from surf, avalanches, earthquakes, volcanoes, waterfalls, calving of icebergs, meteors, lightning, severe weather, and etc.