Editing Light field (section)

===Sound analog===
The analog of the 4D light field for sound is the sound field or wave field'','' as in [[wave field synthesis]], and the corresponding parametrization is the [[Kirchhoff–Helmholtz integral]], which states that, in the absence of obstacles, a sound field over time is given by the pressure on a plane. Thus this is two dimensions of information at any point in time, and over time, a 3D field.

This two-dimensionality, compared with the apparent four-dimensionality of light, is because light travels in rays (0D at a point in time, 1D over time), while by the [[Huygens–Fresnel principle]], a sound [[wave front]] can be modeled as spherical waves (2D at a point in time, 3D over time): light moves in a single direction (2D of information), while sound expands in every direction. However, light travelling in non-vacuous media may scatter in a similar fashion, and the irreversibility or information lost in the scattering is discernible in the apparent loss of a system dimension.