How to specify acoustic fencing

If you’ve ever been involved in specifying acoustic fencing for a project, you might have wondered what makes for truly effective acoustic panels. It may seem that there are plenty of options to choose from, yet sometimes it is not the case that barriers advertised as having acoustic properties really work as effectively as they promise.

Generally speaking, standard timber garden fencing is not capable of adequately reducing noise. Not only do acoustic barriers have to be manufactured in very particular ways to perform optimally in the real world, but their placement with respect to the source of the noise is also critical. At Jacksons Fencing, we have decades of experience designing and producing noise barriers. Below we outline the most important considerations when it comes to specifying acoustic fencing.

Noise reduction comes first

For the best results, acoustic fencing should be designed first and foremost for the sole purpose of reducing noise. While other aspects of design, such as aesthetics, privacy, and security, will certainly affect your decision, they should be secondary considerations; prioritising what is most crucial for your project is important.

Our advice is to watch out for phrases like ‘design life’ as opposed to a guarantee. This is a tell-tale sign that the product in question could fail before its stated lifecycle is up, whereas a full guarantee will mean that even if a fault occurs, you’ll be covered with a replacement product.

Highways and railways

Roadside locations often need acoustic barriers to combat noise disturbance, but there are requirements that mean you can’t just pick anything that claims to be ‘acoustic’. In the UK, any fencing specified for highways and railways must be UK Conformity Assessed, or UKCA-marked, as a whole system. (The UKCA-marking replaces the old CE-marking system post-Brexit for the UK market; as a product marking system it covers most goods previously subject to the CE-marking.)

It’s crucial to note that a fence made out of components that are individually UKCA-marked, does not automatically constitute a compliant barrier system. When specifying roadside acoustic barriers, you should ask for a Declaration of Performance from the manufacturer. Jacksons Fencing is currently the only company in the UK manufacturing UKCA-marked timber acoustic barriers for road application as a whole system.

Noise reduction factors

So what are the material qualities fencing needs for sound to be effectively diminished?

There are two considerations that are absolutely vital – surface mass density and solid construction. In other words, the fence needs to have a certain amount of weight and it needs to form a completely airtight system. When these two factors collide, the bulk of the noise will be stopped from travelling straight through the structure, as it would with a fence not designed for noise reduction purposes.

An effective acoustic fence should be at least 25mm thick and have a mass of 10kg/m2 to prevent noise leaking through the material itself. At Jacksons Fencing, we manufacture our acoustic barriers with timber boards that are 34mm in thickness; in comparison, a normal garden fence would usually be approximately 4kg/m2.

Standard garden fences also tend to be perforated, which is no good for keeping sound out. It’s important for a barrier to have no gaps between any parts, including fence boards or between boards and posts. A capping rail will keep the boards and pales tightly sandwiched together.

Reflective or absorptive?

There are two types of timber acoustic barriers that reduce unwanted noise: reflective and absorptive. So how do you know which one is right for your project?

Reflective barriers are the more commonly used type for large areas, where there’s enough space to reflect and redirect soundwaves away from the protected area. They are straightforward to specify, and a highly effective sound reduction solution for environments like motorways and school playgrounds, but they are not suitable for every application.

If you need to reduce noise levels in confined spaces, for example around air conditioning units or generators, you will require absorptive barriers. In a small space like this, reflective barriers could even make the problem worse by increasing noise, as sound energy ricochets back and forth between two parallel panels. Absorptive panels, on the other hand, are treated with an additional layer of mineral rockwool fibre, which traps and breaks down sound frequency, diffusing sound waves.

It’s important to understand that one type of barrier is not better than the other, they just work for different settings. Therefore each sound reduction solution needs to be carefully tailored for the site in question.

Height & distance

While it’s vital to have a barrier constructed correctly from the right materials, the dimensions are no less important. Both barrier height and the distance between noise source and receiver also influence what will be the most effective choice. Equally, you need to think about the relative height of the source of noise and receiver with respect to the barrier itself. In other words, you need to know where people are likely to be situated in relation to the barrier.

Because of all these variables, each location will require a unique tailor-made solution, and it’s therefore highly recommended that you organise a site survey and a consultation with a professional sound engineer. They will attend your site, take sound readings from various points and at different times of the day to determine what qualities and measurements are needed for the most effective acoustic fencing solution.

Types of timber acoustic barriers

As long as your acoustic panels follow the requirements listed above, their design can vary, but there are some drawbacks to the most common types that are good to keep in mind.

Sometimes acoustic barriers are designed as lap panels, where the boards overlap onto each other. The problem with this is that as a natural material with knots and grooves, timber is difficult to shape into perfectly consistent straight edges. This can sometimes lead to tiny gaps between the pales, allowing sound to leak through. A traditional featherboard design often has the same issue.

At Jacksons, we make our acoustic barriers with a tongue and groove design, which is a standard, neutral look that suits most applications. With this design, it’s crucial that the ‘V’ in between boards is deep enough to counteract any issues with shrinkage, as this will ensure gaps don’t form during the product’s lifecycle.

Depending on your project, you might also want to consider double-sided acoustic barriers. This is a highly effective solution, but not always suitable, as it requires a much larger footprint than normal single-sided solutions.

A tailored solution for your project

From schools to hospitals, and retail/industrial estates to transport hubs, there are many types of places where controlling noise levels is necessary – virtually any space that is at times inhabited by large crowds or contains heavy machinery. But the requirements of a place of worship will be very different to a public space, hotel, bar or casino, or indeed a government office. Getting advice from trained professionals is a crucial step to ensuring your solution is effective.

To find out what we can do for you at Jacksons Fencing, speak to us today.