very low frequency

Very low frequency (VLF) radiation is defined by the ITU to be electromagnetic radiation (EMR) within the frequency range of 3-30 kHz. Its range is between that of the ITU classifications Low Frequency (LF, which is a bit lower than the frequencies commonly viewed in what is termed low frequency radio astronomy) and ultra low frequency (ULF), which has even lower frequency. VLF is generally classified as a lower-frequency portion of the radio spectrum, but definitions of the frequency-range of radio are not unanimous and some would classify VLF as subradio.