Sound insulation index R

Definition and scope

Determination of airborne sound insulation of building elements such as walls, floors, doors, windows, facade elements, facades.

The measurement must be performed in a lab facility without any flanking transmission.

"The results of measurements ... should not be applied directly in situ, without taking into account other factors that influence sound insulation, including the transmission side and the loss factor." Extract NF EN ISO 10140 -1 and 2: 1995

Evaluation method according to NF EN ISO 10140-1 and 2

Expression of results: Calculation of weighted single index Rw (C; Ctr) according to DIN EN ISO 717/1

Consideration of R values per octave between 100 and 3150 Hz with an accuracy of 1/10th of dB.

Vertical displacement of a reference curve by 1 dB jumps until the sum of adverse deviations is the largest while remaining less than or equal to 32 dB.


Rw in dB is then given by the value of the reference curve at 500 Hz.

The terms of adaptation to a spectrum (C and Ctr) are calculated using the reference spectra for:

  • The insulation with respect to neighborhood noise, industrial activities or airport: RA = Rw + C dB 
  • The insulation with respect to the noise of land transport infrastructures: RA,tr = Rw + Ctr dB
Exemple test result