Acoustic ISO 717-1

The R index, standardized by the EN ISO 717-1 standard, evaluates the acoustic quality of a partition, meaning its ability to resist the transmission of airborne sounds. It is measured only in a laboratory and only takes into account direct transmission, excluding lateral transmissions. The R index is expressed in dB(A) and is measured over the entire frequency spectrum from 100 to 4000 Hz.

The calculation of this index is done by shifting the base curve (in blue) dB by dB, until the sum of the unfavorable values (pink point under the green curve) is as large as possible but less than 10 dB across 5 octave bands (32 over 16 third-octave bands).

The Rw value of the partition is the value of the “shifted” (green) curve at 500 Hz.

Two correction indices are used to adjust the Rw index to the characteristics of the noise sources:

• C: correction for sources containing low frequencies (such as fast road traffic, children playing, or household activities).
• Ctr: correction for sources containing a lot of low frequencies (such as urban traffic, distant aircraft, or discotheques).

The acoustic attenuation index R of a partition or door is therefore expressed as: Rw (C; Ctr).

For example, a partition with an Rw (C; Ctr) = 37(-1; -3) indicates an acoustic attenuation of 37 dB for mid-frequency noises, with corrections of -1 dB for fast traffic noise and -3 dB for urban traffic noise.

Download our brochure on the EN ISO 717-1 standard to learn more about the tests and how the overall Rw value of a door is determined.