# Translations:Attenuation/5/en

The energy of a wave in a homogeneous material is proportional to the square of its amplitude (which can be expressed in terms of pressure, particle velocity, or particle acceleration). A point source produces a spherical wave that spreads out from the source. The energy is distributed over the area of the sphere, which increases as the square of the sphere’s radius. Thus, the wave’s energy per unit area varies inversely as the square of the distance from the source. The wave’s amplitude is proportional to the square root of the energy per unit area. Thus, the wave’s amplitude is inversely proportional to the distance the wave has traveled. *Spherical spreading* — that is, the loss of amplitude because a wave spreads out — is one cause of attenuation. Such energy loss is called *geometric divergence*.