Approximate specific acoustic insulation (R’)

Professional Definition

Approximate specific acoustic insulation (R’) is the acoustic insulation of a partition measured in field conditions (in a building), taking into account the lateral sound transmission through paths other than the direct path through the partition.

The formula for R’ is based on the difference in sound pressure levels in the transmitting and receiving rooms, corrected for the acoustic absorbency of the receiving room and the surface area of the partition. A key difference from the laboratory indicator R is that R’ is always a value less than or equal to R, because it takes into account the acoustic energy transmitted through side walls, ceilings, ventilation ducts, and leaks (so-called lateral transmission).

Acoustics in Simple Words

Think of a wall as a dam on a river. The laboratory indicator R tells us how airtight the concrete of the dam is. In contrast, the approximate specific acoustic insulation R’ is the situation where the dam is placed in a valley. It turns out that the water (sound) does not penetrate through the concrete but leaks around the sides – through cracks in the rock, under the foundations, or over the top. R’ measures how much water was actually managed to be retained in the valley, considering not only the quality of the dam itself but also how it was connected to the surroundings.

Summary

R’ is the most important parameter when assessing the acoustics of residential and office buildings. It determines whether the building meets legal standards and whether residents will enjoy the comfort of silence.