Calculating weighted noise reduction (DnTw) from reduction Rw (Sound insulation)

Equations

For lightweight walls, you can calculate this using the following equation:

$R_\text{w} = D_{\text{nTw}} - 10 \log_{10} d + 14$

For heavyweight walls, use:

$R_\text{w} = D_{\text{nTw}} - 10 \log_{10} d + 11$

Only the value at thee end of these changes.

Look up table

For general floor and wall partitions, use the following look-up table:

Floors

If we are considering floors, the we frequently have a ceiling height of between 2.5 and 3 m. If this is the case, then we can calculate a simple subtraction value to convert:

To obtain the required Rw value from the DnTw value, simply subtract the value in the table above. For example, for a lightweight ceiling with a height of 2.5 m with an Rw of 50 dB, the DnTw value will be 40 dB DnTw.