Sound reduction index R
Sound reduction index R is a logarithmic value that quantifies the level of sound insulation provided by building components. R depends on the frequency and angle of incidence of the sound waves. The sound reduction index describes the sound insulation capacity of a given material. It is calculated as the ratio of the total incident sound intensity to the amount of sound intensity that the material lets through. A high R value equals a low transmission factor and hence a high sound insulation effectivity.