ultra low frequency

Ultra low frequency (ULF) radiation is defined by the ITU to be electromagnetic radiation (EMR) within the frequency range of 300 Hz to 3 kHz. It is considered within the lower-frequency end of the radio spectrum, or beyond (i.e., subradio). It falls between super low frequency (SLF) and very low frequency (VLF).

Note that in the sciences, the term ultra low frequency (ULF) is often used for extremely low frequencies without regard to the ITU specification, e.g., meaning frequencies less than a kHz or even meaning on the order of a Hz. The term may be used for EMR, sound waves, or seismic waves. Example areas where such waves are of interest are geophysics and space weather.