Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths from 100,000 to 10,000 kilometers. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower frequency electro...
[n] - below 3 kilohertz
That portion of the radio frequency spectrum from 30 to 3000 hertz. See also: Frequency.
ELF noun below 3 kilohertz
any frequency between 30 and 300 hertz. Abbr.: ELF, elf