Calculating the decibel reduction of a soundwall
How many decibels does a soundwall or acoustic barrier actually reduce? The short answer: 10 to 25 dB when the wall is correctly dimensioned. The longer answer depends on three principles that each contribute: mass, geometry and absorption.
The three principles of noise reduction
The noise reduction of an acoustic wall results from three effects working together. Understanding them lets you estimate which wall your situation needs.
Physical Obstruction
A solid barrier blocks the direct sound waves between the source and the receiver.
Sound Absorption
A porous core (coconut fiber, rock wool) traps sound energy instead of reflecting it.
Sound Diffraction
Remaining waves must bend over the barrier, a detour that weakens the sound.
Path length difference: why height matters so much
The wall must interrupt the straight line between source and ear. The bigger the "detour" the noise has to take to go over or around the wall, the greater the reduction. This is called the path length difference. Doubling the path difference yields roughly 3 dB extra reduction.
Rules of thumb in dB for your situation
In practice our acousticians use these reference values to make a first estimate.
- Light wooden fence (~5 kg/m², 1.8 m high): 3 to 5 dB
- Solid concrete wall without absorption (1.8 m): 8 to 12 dB
- Noise-Reducer soundwall (2.5 m, with absorption): 15 to 20 dB
- Combination soundwall 4 m + Kokowall absorption close to the source: 20 to 25 dB
- Industrial enclosure around the noise source: 25 to 40 dB
What does a dB reduction feel like in practice?
Decibel is a logarithmic scale, so 10 dB less feels like a halving of the noise. A well dimensioned soundwall brings the volume of a busy road back from an annoying level (around 65 dB) to a pleasant background noise (around 50 dB). Ask us for a free simulation of your specific situation.
Frequently asked questions about decibel reduction
How do I measure my current noise exposure?+
You can get a first indication with a free decibel app on your smartphone, but an official measurement requires a class-1 meter and a certified acoustician. We carry out such measurements as part of our advice.
Is a 5 dB reduction noticeable?+
Yes, but only slightly. 5 dB feels like "a bit quieter". From 10 dB it feels "clearly quieter". We always aim for at least 10 dB to justify the investment.
Does absorption or isolation work best?+
Both. Isolation (mass) blocks noise trying to pass through the wall. Absorption (porous layer) prevents noise from bouncing back and reaching you via another route. Our Kokowall combines both.
Request your quote today
Our experts will be happy to advise you on the best solution for your situation. Contact us for a non-binding conversation.