Mass law
An approximation that describes the sound transmission loss TL (sound reduction index R) of a limp, flexible barrier in terms of mass density and frequency. For each doubling of the weight or frequency of a partition, mass law predicts a 6 dB increase in TL (or R).
For most building elements the mass law is a valid approximation only in a limited frequency range and other effects as the decrease of the sound reduction at the critical frequency has major influence on weighted values as Rw .