Airborne Sound Insulation

 The sound insulation is normally expressed with the sound reduction index R. R depends on the frequency of the sound passing through the element and is measured in 1/3 octave bands according to ISO 140.

According to ISO 717 a rating of the frequency depending sound insulation results in a single number value Rw and adaption terms C and Ctr can be performed.

Definition:

Reduction index (but diffi cult to measured)

Meassurement (laboratory):

Reduction index

  The sound rating according ISO 717 uses a reference curve, which is shifted up or down until the sum of the unfavourable deviations between measurement result and shifted reference curve is a maximum, but still less or equal 32 dB. The single number value Rw is the value of the shifted reference curve at 500 Hz.

Sound reduction index:

  Example - facade:
Rw (C ; Ctr)=41 (0 ; -5) dB
External traffic noise with 65 dB(A) will be reduced with 41 + (-5)=36 dB to 65-36=29 dB(A) behind the facade.