Composite Wall Sound Insulation Calculator (Wall with Window, Door or Gap)
The sound reduction of a wall made of several parts — wall, window, door, vent or open gap — from their areas and their own dB ratings, and which part lets most of the sound through.
Results
The dashed line marks the value you entered.
What this tool does
Sound reductions cannot be averaged in dB: the parts add up as transmitted sound energy, so the weakest element dominates. A 50 dB wall with a tenth of its area as a 30 dB window comes out near 40 dB, not 48, and a gap of just 1 % of the area caps the whole wall at about 20 dB however good the rest is — which is why sealing gaps and doors matters before upgrading the wall. The result is for one frequency or one single-number rating at a time; use the same kind of figure for every element.
Formula
R = −10 log₁₀ [ Σ(Sᵢ × 10^(−Rᵢ/10)) ÷ ΣSᵢ ] (area-weighted sound transmission)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
s1 | Area of the main wall | m² |
r1 | Sound reduction of the main wall | dB |
s2 | Area of the window | m² |
r2 | Sound reduction of the window | dB |
s3 | Area of a third element (door, vent, gap…) | m² |
r3 | Sound reduction of the third element (0 for an open gap) | dB |
RC | Sound reduction of the whole wall | dB |
LS | Lost compared with the wall alone | dB |
H1 | Share of the sound that gets through the wall | % |
H2 | Share of the sound that gets through the window | % |
H3 | Share of the sound that gets through the third element | % |
Worked example
- Area of the main wall10 m²
- Sound reduction of the main wall50 dB
- Area of the window3 m²
- Sound reduction of the window32 dB
- Area of a third element (door, vent, gap…)2 m²
- Sound reduction of the third element (0 for an open gap)28 dB
- Sound reduction of the whole wall34.6 dB
- Lost compared with the wall alone15.4 dB
- Share of the sound that gets through the wall1.9 %
- Share of the sound that gets through the window36.7 %
- Share of the sound that gets through the third element61.4 %
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.