An acoustic barrier works by being heavy enough to stop sound passing through it, solid enough to have no gaps, and tall and long enough to break the line of sight between the noise and the listener. Get any one of those three wrong and the barrier underperforms, regardless of what the product datasheet says.
Acoustic fencing is usually specified because a planning condition demands it. Here is what drives the specification, and where the numbers come from.
What actually determines acoustic performance
Surface mass comes first. To stop sound transmitting straight through, a barrier needs meaningful weight. A standard domestic timber fence is around 4 kg per square metre, which is nowhere near enough. Guidance for school sites recommends a close boarded fence of not less than 16 kg per square metre.
There are diminishing returns. Past roughly 15 to 16 kg per square metre, performance is limited by sound diffracting over the top rather than passing through. That is why a well built close boarded timber barrier often performs much like a concrete wall of the same height. Specifying something heavier rarely buys what people expect.
Gaps destroy performance. The barrier must be imperforate. Hit and miss fencing, slatted fencing and planting are not acoustic barriers, because sound simply passes through the openings. Gaps at the base, between panels or around posts undo the rest of the design.
Hedges and trees do not work. This surprises clients regularly. A band of trees is a visual screen, not an acoustic one. The recognised approach is to put a real barrier inside the planting so you get the acoustic performance and the appearance together.
Line of sight and length matter as much as height. Sound travels in straight lines, so the barrier has to interrupt the path from source to receiver, and extend far enough sideways that noise does not simply flank around the ends.
One useful rule of thumb from school design guidance: noise levels can be reduced by up to about 10 dBA at positions close to an acoustic screen. Where the ground allows it, an earth bund acting as the barrier with planting for appearance is generally regarded as the best solution of all.
The standards behind the numbers
When a supplier quotes acoustic performance, it should trace back to the BS EN 1793 series, which sets test methods for road traffic noise reducing devices:
- Sound absorption is described by the descriptor DLα.
- Airborne sound insulation, meaning how much sound is stopped from passing through, is described by DLR.
Those two descriptors are what let you compare products like for like. BS EN 14388 is the product specification standard for road traffic noise reducing devices, and the BS EN 1794 series covers the non acoustic side: wind and static loading, safety and durability.
A practical distinction worth understanding is reflective versus absorptive. An absorptive facing matters where reflections would make things worse on the opposite side, for example where barriers face each other across a road or face housing.
What usually triggers a barrier
Residential planning
Noise policy in England works through two thresholds: the lowest observed adverse effect level and the significant observed adverse effect level. Where an impact falls between the two, reasonable steps must be taken to mitigate and minimise it, and that is very often where acoustic fencing is conditioned. There is deliberately no single national number, because it depends on the source, the receptor and the time of day.
For internal conditions, BS 8233 gives guideline levels of 35 dB for living rooms and bedrooms during the day, 40 dB for dining rooms, and 30 dB in bedrooms at night.
Schools and nurseries
Building Bulletin 93 sets indoor limits, typically 35 dB for classrooms in new build. The external criteria sit in the companion IOA and ANC design guide, which recommends that noise in unoccupied playgrounds and playing fields should not exceed 55 dB, with at least one area suitable for outdoor teaching below 50 dB. Where a site cannot achieve that, the guidance is explicit that acoustic screening should be used to reduce levels as far as practicable.
Note this cuts both ways. Local authorities also assess noise from schools affecting neighbours, which is its own common trigger for fencing.
Sports pitches
For artificial grass pitches and MUGAs there is a defensible national target: Sport England guidance works to 50 dB LAeq over one hour outside residential properties and within external living areas. Two details from that guidance are worth passing to any installer:
- Build the acoustic barrier outside the perimeter fence, so it does not get hit by balls and become a noise source itself.
- Clamp panels securely with resilient fixings, because rattling from ball impacts is a frequent complaint.
A 3 m barrier can bring levels below the target at ground level, but it becomes much less effective for receptors higher up, such as flats, because they can see over it.
For padel courts there is currently no national noise standard at all. The LTA’s construction guidance advises that where a residential property is within 50 m, noise and light surveys by specialist consultants are likely to be required. Barrier specification therefore follows whatever the consultant’s assessment and the resulting condition demand.
The point almost everyone misses: planning permission
Under permitted development rights, a fence, wall or gate is normally allowed up to 1 metre where it adjoins a highway used by vehicles or its footpath, and 2 metres elsewhere.
Acoustic fencing is typically 1.8 m to 3 m or more, because height is what buys performance. So most acoustic fencing above 2 m requires planning permission in its own right, even when it is being installed to satisfy a noise condition. Permitted development also does not apply to listed buildings and their curtilage, or where rights have been removed by an Article 4 direction or a condition.
It is worth resolving that before the barrier is designed, not after.
Specifying one sensibly
- Get the acoustic assessment first. The condition or report should tell you the target and the receptor.
- Fix height and length from the line of sight geometry, not from a catalogue.
- Check surface mass, and check the design is genuinely imperforate, including at the base.
- Decide reflective or absorptive based on what is opposite.
- Confirm the planning position on height before ordering.
We manufacture and install acoustic panels and barriers as part of our wider metalwork capability, and we are happy to work from an acoustic consultant’s report rather than guess at a specification.
Frequently asked questions
Does acoustic fencing need planning permission?
Usually yes. Permitted development generally allows 2 m, or 1 m adjacent to a vehicular highway, and effective acoustic fencing is normally taller than that.
Will trees or a hedge reduce noise?
Not meaningfully. Planting is a visual screen. The usual solution is a solid barrier placed within planting so you get both.
How much noise reduction can I expect?
It depends entirely on geometry and the receptor. Close to a well designed screen, reductions of up to around 10 dBA are achievable. Anyone quoting a single figure without knowing the site layout is guessing.
Written by Daryl Griffiths, Managing Director, MG Group. Sources: BS EN 1793 and BS EN 14388 series, BS 8233:2014, the Noise Policy Statement for England, Building Bulletin 93 (2015) and the IOA/ANC Acoustics of Schools design guide (2015), Sport England AGP acoustics guidance (2015), LTA padel court construction guidance (2025), and the Town and Country Planning (General Permitted Development) (England) Order 2015. Checked August 2026. General guidance; site specific acoustic assessment should always govern.
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