What is Rw?
Rw is the ‘weighted sound reduction index.’ It is a number used to rate the effectiveness of the glass as a noise insulator and is measured in decibels (dB). It also takes into consideration a correction factor for the response of the human ear. For example, if a busy street has a noise level of 75dB and the required level of noise in a room is 40dB, the Rw value of the required glass is 35dB. Glass types with a Rw value greater than 35dB can then be offered as solutions.
It is worth remembering that every 10dB reduction is perceived by the ear as being half as loud, so that a 20dB noise reduction would reduce the perceived noise by 75%.
Sound reduction figures
Sound reduction figures for 28mm standard double glass:
|4/20/4||Standard double glass||20.00 kg/m2|
|6/16/6||Standard double glass||30.00 kg/m2|
|6/12/10||Double glass with different glass thickness|
|6/16/6.4||Laminated double glass|
|6/16/6.8||Acoustic Laminated double glass||39 dB|
If you are looking to achieve a sound reduction with a standard 28mm glass unit, the maximum sound reduction index (Rw) is 39 dB. : 28mm overall. If they want a high sound reduction, it is not always possible within this 28mm available space and often there may be a compromise in the U-values.