How much does an extra layer of plasterboard help?

 

*For a typical 200mm wide brick wall the sound reduction index Rw is 54 dB

ST10

 

ST11

 

To gain one dB of reduction we need to add at least an inner layer of plasterboard of 23mm.

In order to obtain an extra dB more, an inner layer of plasterboard of 65mm is needed, which makes this a non-practical method to increase the sound reduction.