Temporary Acoustic Barriers on Construction Sites: What Actually Works
Quick answer
A properly specified temporary acoustic barrier can cut construction noise by 10 to 20 dB at a neighbouring facade — enough to turn a nuisance into a normal working site. The performance depends almost entirely on height, mass and where the barrier sits between the source and the receiver.
Key takeaways
- Barriers work on the line of sight: if you can see the plant, the barrier is doing less than it could.
- 10–20 dB reduction is realistic at a nearby facade with a correctly sized, sealed barrier.
- Low frequency piling noise is harder to block than the mid and high frequencies of tools and alarms.
- Barriers do nothing for ground-borne vibration, which needs source-side mitigation.
Acoustic barriers are the most common mitigation measure on noisy construction sites, and also the most commonly misrepresented. A barrier that is too short, poorly sealed or in the wrong place can reduce noise by almost nothing while appearing on a mitigation plan.
How a barrier reduces noise
A barrier does not absorb the site's noise. It interrupts the path between the source and the listener, forcing sound to travel over the top edge. That detour is longer than the direct path, and the difference — the path length difference — is what produces the reduction.
The practical consequence: a barrier only works if it breaks the line of sight. If a resident can see the piling rig over the top of the panels, the barrier is contributing very little.
What performance is realistic
For a correctly specified barrier close to the source:
| Situation | Realistic reduction |
|---|---|
| Line of sight fully broken, barrier 3–4 m high near the plant | 10–15 dB |
| Taller barrier or plant in a compound with returns | 15–20 dB |
| Barrier present but line of sight not broken | 0–5 dB |
| Low-frequency impact noise from piling | 3–8 dB less than the figures above |
Where barriers fall short
- Low frequency. Impact piling produces strong energy at 20–100 Hz, which diffracts over and around barriers far more readily than mid frequencies.
- Vibration. Barriers reduce airborne noise only. Ground vibration passes underneath entirely and is dealt with by choosing a different piling method or interrupting the vibration path.
- Gaps. A 50 mm gap in a run of panels can dominate the performance of the whole barrier. Sealing at ground level and between panels matters as much as the panel specification.
- Height and distance. A barrier half a metre too short at close range can lose most of its benefit.
What to ask a site to provide
If you are a contractor drawing up a Section 61 application, or a resident reviewing a mitigation plan, these are the questions that separate a real barrier from a line on a drawing:
- What is the barrier height, and does it break the line of sight from the nearest dwellings?
- What surface mass do the panels have, and are they sealed at ground level and at joints?
- How close is the barrier to the plant, and does it return around the compound?
- What reduction has been predicted, and by whom?
Temporary acoustic barriers are a mature technology, widely manufactured in New Zealand and Europe, and they work well when specified honestly. Supported by Hushtec, a New Zealand manufacturer of temporary acoustic barriers, this site exists to help residents and contractors have that honest conversation.
Frequently asked questions
How much noise does a temporary acoustic barrier reduce?
A realistic reduction is 10–15 dB at a nearby facade when the barrier fully breaks the line of sight between the plant and the listener, and up to 20 dB with a tall barrier or an enclosed compound. If the line of sight is not broken, expect very little benefit.
Do acoustic barriers help with piling noise?
Partly. They reduce the airborne mid and high frequencies well, but impact piling carries strong low-frequency energy that diffracts over barriers. For piling, barrier performance is typically several decibels lower than for tools or plant engines.
Do barriers reduce vibration?
No. Barriers act on airborne sound only. Vibration travels through the ground beneath the barrier and has to be managed by changing the piling method or the operating regime.