Mass Law Sound Insulation Calculator
How much airborne sound a single solid wall or panel blocks at a given frequency, from its mass per square metre, by the mass law.
Results
The dashed line marks the value you entered.
What this tool does
For a single solid layer, sound insulation depends almost only on mass: double the mass per square metre, or the frequency, and it improves by about 6 dB. That is why heavy masonry insulates well and why low bass passes through everything. Real walls fall short of the law near their coincidence frequency, and leaks around doors, sockets and joints, or sound going round the wall through the floor and ceiling, often matter more than the wall itself. Two separated layers with an air gap and absorbent can beat the mass law by a wide margin.
Formula
R ≈ 20 log₁₀(m × f) − 47 dB (field-incidence mass law, m in kg/m², f in Hz)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
m | Surface mass of the wall | kg/m² |
f | Frequency | Hz |
tg | Sound reduction you want | dB |
R | Sound reduction at that frequency (mass law) | dB |
R2 | With twice the mass | dB |
MT | Surface mass needed for the target | kg/m² |
Worked example
- Surface mass of the wall200 kg/m²
- Frequency500 Hz
- Sound reduction you want50 dB
- Sound reduction at that frequency (mass law)53.0 dB
- With twice the mass59.0 dB
- Surface mass needed for the target141.6 kg/m²
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.