lowfrequency

Low frequency is a term used across science and engineering to describe the lower end of a system’s usable spectrum. What counts as “low” depends on the context, but it generally refers to signals with longer wavelengths and lower energy than midrange or high-frequency content. Low frequencies often have longer impulse responses and are more susceptible to environmental properties, such as air, water, and building materials.

In audio and acoustics, low frequencies typically span roughly from 20 Hz up to a few hundred hertz, with sub-bass below about 60 Hz. Reproducing these frequencies reliably requires larger transducers because their wavelengths are long. In signal processing and electronics, low-frequency signals vary slowly in time and concentrate near 0 Hz in the spectrum. They are associated with circuits that have long time constants and may be passed by high-pass filters with low cutoff frequencies, while rapid changes (high frequencies) are attenuated.

In radio communications, the term low frequency has a more specific meaning. The low-frequency (LF) band generally covers 30 kHz to 300 kHz and is used for long-range navigation, time signals, and certain submarine communications. Very-low-frequency (VLF) is 3–30 kHz. Propagation in the LF and VLF bands relies largely on ground-wave and, under certain conditions, sky-wave modes, making reception less dependent on line-of-sight paths but more sensitive to ground conductivity and atmospheric conditions. Antenna sizes at these frequencies are correspondingly large.