Noun
English Wikipedia has an article on:infrasoundWikipedia
infrasound (countable and uncountable, plural infrasounds)
(physics) Sound waves having a frequency below the human audible range (below about 20 Hz).
Echoes of Mogul's experimental infrasound detection of nuclear tests exist today in ground-based detectors, part of so-called Geophysical MASINT (Measurement And Signal INTelligence). Source: Internet
During nighttime, giraffes appear to hum to each other above the infrasound range for purposes which are unclear. citation Reproduction and parental care Male giraffe mounting a female. Source: Internet
Giraffes also snore, hiss, moan, grunt and make flute-like sounds, and possibly communicate over long distances using infrasound citation —though this is disputed. Source: Internet
Rotary woofers are able to efficiently reproduce infrasound frequencies, which are difficult to impossible to achieve on a traditional speaker with a diaphragm. Source: Internet