Infrasound is just sound beneath the human’s listening to vary, sometimes below 20 Hz. At such low frequency a true sound wave causes the local strain to go up and down and is distinguished from air movement. Patent for a double bass reflex loudspeaker enclosure design supposed to supply infrasonic frequencies ranging from 5 to 25 hertz, of which conventional subwoofer designs will not be readily capable. Numerous animals produce and use sounds in the infrasonic vary.
Infrasound could be considered a slow, periodic rumbling – it is generated by massive processes resembling avalanches, volcanoes, tornadoes, ocean waves, earthquakes , and meteors...