Weighted Sound Reduction Index Rw
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Weighted Sound Reduction Index Rw

When specifying the acoustic performance of a partition in a more general manner, it can be useful to describe the sound insulation by a single number. The weighted sound reduction index, Rw , is a rating method given in EN ISO 717-1. This standard fits a standard reference curve to the measured sound reduction index curve

In EN ISO 717-1, a rating method is also given where the Rw value is completed by two C-terms which are applied to two models of the noise spectra for various types of noise. These two terms, Rw + C and Rw + Ctr, also include the frequency range 100 – 3150 Hz but can be extended to 50 – 5000 Hz. As industrial and traffic noise often have high sound levels which are also below 100 Hz, it is recommended that the extended frequency area is used.

The summary value, Rw + C, gives the reduction value in dBA for a spectrum with a level which is equally high in all third-octave bands. This can be used for:

Living activities (talking, music, radio, TV)
Railway traffic at medium and high speed
Highway road traffic travelling at speeds in excess of 80 km/h
Jet aircraft at a short distance
Factories emitting mainly medium and high frequency noise

The summary value Rw + Ctr also gives the reduction value in dBA, spectrum with low-frequency dominance such as:
Urban road traffic
Railway traffic at low speeds
Disco music
Factories emitting mainly low and medium frequency noise
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