In acoustics, a free field is a situation or space in which no sound reflections occur.[3] In a free field, sound is attenuated with increased distance according to the inverse-square law.[1] In nature, free field conditions occur only when sound reflections from the floor can be ignored, e.g. in new snow in a field, or approximately at good sound-absorbing floors (deciduous, dry sand, etc.)Free field conditions can be artificially produced in anechoic chambers.In particular, free field conditions play a major role in acoustic measurements and sound perception experiments as results are isolated from room reflections.With voice and sound recordings, one often seeks a condition free from sound reflections similar to a free field, even when during post-processing specifically desired spatial impression will be added, because this is not distorted by any sound reflections of the recording room.[1] The sound intensity and pressure level of any point in a free field is calculated below, where r (in meters) is the distance from the source and "where ρ and c are the air density and speed of sound respectively.[1] To calculate for air pressure, the equation can be written differently:[1][1] Measuring the sound pressure level at a reference distance (Rm) from the source allows us measure another distance (r) more easily than other methods:[1]
