Far-field

Far-field refers to the region away from a source, such as a sound or electromagnetic wave, where the waves spread out and behave predictably. In this area, the wavefronts are approximately spherical or planar, and the strength of the waves diminishes with distance in a specific way, making analysis easier. For example, at a distance far from a loudspeaker, sound waves can be considered to be spreading evenly, simplifying calculations. Far-field typically starts beyond a certain distance known as the far-field zone, where detailed near-source effects become negligible.