VLF range

Also called infrasound, low-frequency sounds stand for sound waves with a frequency below the lower limit of audibility (which is generally at about 20 Hz). Low-frequency sounds are all sounds measured at about 500 Hz and under.

Ultra-Low Frequency (ULF) waves are waves with a period between roughly 1 and 1000 seconds that are usually measured with magnetometers on the Earth’s surface or on spacecraft . They are, however, not exclusively found in near-Earth space, but also around other planets and in interplanetary space.

Ultra low frequency (ULF) is the ITU designation for the frequency range of electromagnetic waves between 300 hertz and 3 kilohertz , corresponding to wavelengths between 1,000 to 100 km.