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Every year the number of vehicles on our roads is growing. Even where there were no special problems with noise from cars before – in summer cottages. In the private sector, this is becoming a problem. Willy-nilly, you think that you need not an ordinary, but a noise-absorbing fence. What is it, how to make it and we will discuss.
Protection of the house / site from noise: types of soundproof fences
There are two methods of dealing with sound waves – absorption and reflection. If we talk about fences, they also absorb noise and reflect it. More effective absorbing – expensive pleasure. Cheaper reflectors, but they provide only basic protection, not guaranteeing silence at all. After all, the sounds don’t go anywhere. They just bounce off and go the other way. But having found a similar barrier, they can “return”. Yes, they will lose power, but only a little. Nevertheless, there are several techniques that allow you to achieve good results even with reflective fences.
Soundproofing for fences
Noise-reflecting fences are made of materials that have a high reflection coefficient of sound waves. These are brick, concrete, monolithic polycarbonate (without cavities) or plexiglass. This is not to say that such a fence will very effectively protect the site from noise. At the proper height, it will slightly reduce the sound level, but you should not hope for a significant decrease.
An ordinary fence, even if made of brick or concrete, will reduce noise by 5 dB. This is not so little, but far from always enough. To improve efficiency, increase the height of the fence. Each additional meter in height is approximately 1,5 dB of noise reduction.
Comparison of fences
Brick fences due to the greater mass are more effective. They are durable but expensive. Considering that for high-quality noise protection, the height of the fence should be at least 2,5 meters in height (or even higher), and not a quarter, or even half a brick thick, it is understandable why they are trying to find cheaper options. Usually these are concrete fences or filled with polycarbonate and plexiglass. Moreover, polycarbonate is more often used, since plexiglass, with the same thickness, has a higher cost.
One of the most effective in terms of sound protection is gabion. Due to the inhomogeneous filling and large mass, it is really effective. But imagine that you need to build such a wall 2,5 meters high …
Concrete fences are relatively inexpensive, but not everyone likes them. And it’s hard to find quality ones. Due to the porous structure, concrete partially absorbs sounds, partially reflects. And now fashionable design like masonry additionally scatters sounds. So the option is relatively good.
If a brick and concrete fence does not suit you, they remain filled with plexiglass or polycarbonate. It is not worth hoping that such a fence will greatly contribute to silence. The sound wave will not disappear, but will only be reflected. If you have a neighbor’s house opposite, then they will receive additional noise. It won’t improve the relationship.
And if the neighbors have the same polycarbonate fence, then you will be left with almost the same noise level as without a fence at all. If you really want to reduce the level of sounds in the area, either put up a brick / concrete fence, or make a noise-absorbing fence.
Noise absorption
The noise-absorbing fence has other properties. It dampens the power of sound by absorbing its energy. This is a more efficient, but also more expensive technique to implement. Panels are used that consist of several layers with different characteristics or fibrous materials.
The idea is that sound waves, falling into a loose, porous material, are repeatedly reflected. With each reflection, some energy is lost. The output is a significant reduction in sound level. This is if we talk about how fibrous materials work. When using noise protection panels, the level drop also occurs when passing through several layers of materials with different characteristics.
The cheapest noise absorbing fence
The simplest version of a noise-absorbing fence is a solid wooden fence with wooden planks stuffed from the side of the noise source. The slats are arranged in a herringbone pattern or at some intervals parallel and perpendicular to the ground. These strips create additional guides for dispersing sound waves.
Another option for an inexpensive fence with good sound absorption is a double wooden fence (pictured above on the right). Boards can be stuffed with a small gap, but the second row should cover these gaps. Moreover, the gap falls in the middle of the board of the next row.
You can choose any of the ways to form the filling of a noise-absorbing wooden fence. But for good sound protection, the fit of the boards must be perfect. There should not even be small gaps. Planks (pictured at the top left) can be used precisely to close the joints and possible gaps.
There is another technique for building a fence, which gives a very good noise reduction. The boards are installed horizontally, but not end-to-end, as we are used to, but at a slight angle. The bottom edge of the next board overlaps the edge of the one below. It also turns out some “herringbone”, but from the boards, and not from the planks. This fence is also called “American”.
For regions with a low price for wood, these are the simplest and cheapest noise-absorbing fences. It’s hard to find something better for a summer residence. But the disadvantages are the same: the need for care to maintain an attractive appearance. If you like the idea, but don’t smile at caring for wood, you can do the same, but from WPC. This is a wood-polymer composite. It looks almost like wood, but is devoid of its flaws. If you use composite decking without voids, you will get good soundproofing characteristics. Some of the sound will be reflected, some will be absorbed.
Sound reflective panels for fences
If we talk about more effective sound absorption, then the noise-absorbing intake sections are a multi-layer structure. These are panels made of plastic or metal, between which a material with a chaotic arrangement of fibers is laid.
Usually, this is one type of mineral wool (acoustic) in mats or panels. The outer part of the sound-absorbing panel is metal or plastic, and they are reflectors. In order to more effectively absorb sounds, perforations are made on the side of the noise source. The wall, which is directed inward, is made of smooth metal.
Anti-noise screen – a combination of techniques
We already know that there are fences with noise reflection, and there are with absorption. Efficiency can be improved by combining techniques. Some of the noise will be reflected, some will be absorbed.
Effective noise protection fences consist of different parts. Usually at the bottom is a sound-absorbing screen, at the top is a reflective one. And they call this whole structure “acoustic screens”. For greater efficiency, the reflective part can be tilted towards the noise source. This is technically more difficult, but it increases the size of the “silence zone”.
Features of the construction of a noise-absorbing fence
Before you start building a noise-absorbing fence, you need to find out if your area has restrictions on the height of fences in private areas. They are usually installed by local authorities. The second point is to enlist the support of neighbors. Lawsuits from neighbors for a high fence are not the best prospect.
Racks and foundation
Above were legal and organizational issues. Now for the technological details. Since the soundproofing fence usually has a large height, wind loads will be significant. This should be considered when choosing racks. Take with a good margin of safety. Otherwise, with gusts of strong wind, your fence will collapse. It has great height and considerable mass. If it falls, it can even damage the houses opposite.
For the same reason, when building a soundproof fence, poles / racks should be buried deeper. Additional spacers can be made in the buried part, which will increase the stability of the support. If you plan to install a fence on the foundation, it must also be done taking into account high wind loads.
For better noise isolation
A couple of points about soundproofing. As a rule, a noise-absorbing fence consists of posts / racks and infill. For maximum protection, there should be no gaps between the posts and the infill. Stone/brick/concrete posts can even be grooved for infill frames. Or simply insert the filling shields into the recesses made.
If you plan to use metal racks, then an I-beam is more suitable than traditional pipes. It is also better in terms of bearing capacity, and it is easy to achieve the absence of gaps. Yes, it is more expensive, but it is it that is used in the construction of high anti-noise fences. By the way, horizontal jumpers (at least supporting ones) are also made from a channel with a normal wall thickness. Pillars and lintels, by the way, can also be made from a channel jointed with backs. Get even more “powerful”.
It is better to make the upper sound-reflecting part not vertical, but inclined towards the noise source. Ideally rounded. In this case, the reflected waves will “fall” close to the fence, which will improve the absorption situation. But rounding is quite difficult to do and not with all materials it is possible. Just tilting at a slight angle (22-24°) is good.
If, in addition to noise, vibration is also a concern, vibration damping pads should be used during installation. In the simplest case – pieces of rubber, but for a more professional approach – buy special ones. In case of strong vibration, it will be necessary to install vibration damping elements when pouring the foundation. All this will give a decoupling from vibrations and a low component of sound waves.
What to use to dampen sounds
The best sound absorption characteristics have a special basalt acoustic wool, but it is afraid of moisture. To protect it from moisture, you will need to pack it in a moisture-proof membrane. Moreover, the membrane should transmit sounds well. And the packaging must be airtight, which is not so easy to achieve. In general, the option will turn out to be good in terms of characteristics, but expensive. Acoustic stone wool is expensive, the membrane too.
It is cheaper to use mineral wool (mineral wool). She is not afraid of getting wet, but she is bad to work with. Even in protective clothing, microfibers penetrate everywhere. But more economical, albeit somewhat worse in performance.
There is another option – a soundproof membrane. This is relatively new material. It is sold in rolls, has a thickness of 3-8 mm, while reducing the noise level is at least 40 dB. Some species are frost-resistant, not afraid of moisture. So they are suitable for fences. But the price is not always humane.
Some advise to fill the soundproof fence panels with expanded clay. It is porous, dampens sounds well. It’s like that. But it is very hygroscopic. But, worse, it does not give moisture well. If you plan to use it to dampen sounds, the design will need to be thought out so that there is good ventilation.
How to make an ordinary fence soundproof
You can make a noise-absorbing fence, in principle, from any fence. After all, more often they are trying to modify existing fences. Mesh in this regard is almost hopeless – almost everything will have to be changed. After all, neither the racks nor the filling are designed for loads. An exception is a gitter mesh, to which polycarbonate can be screwed, which will reflect sounds. However, you will need to mount it without the slightest gaps and from the very ground level. But this is on soils with good bearing capacity, without a tendency to heaving (on clays and loams it is better not to).
You probably already understood how to finalize the wooden one – close all the cracks with planks, increase the height, if possible. You can grow not only wood. You can put polycarbonate sheets over the wooden one. We’ll have to grow the racks. And better – at an angle of 20-24 °. Polycarbonate will reflect sound, wood will absorb it.
General ways to increase the level of soundproofing characteristics of fence sections
How else can the sound-absorbing characteristics of an existing fence be improved? There are options:
- The profiled sheet can be closed with mineral wool (preferably glass wool). From the side of the courtyard, you will have to cover it with something that does not reflect sounds very well. Otherwise, you will lose part of the effect. This “something” could be: wood, OSB, composite decking. Other options are membranes or fiberglass.
- A sound-absorbing membrane can be attached to any filling. It will also need to be closed with something, but for reasons of safety and integrity. Although materials with high sound reflection should not be used either.
Adding a Membrane - If the fence is not too high, add heights – not necessarily from the same material. You can reduce the noise level on the site if you add monolithic polycarbonate along the top of the fence. As has been said many times, it is better to install it at an angle to the sound source.
- If there are gaps between the filling of the sections and the posts, figure out what and how they can be closed.
All this will help to improve the noise situation in the area. There is also a simple technique, but it takes time: plant plants with a dense crown along the fence. Foliage perfectly diffuses sounds. For example, you can land pyramidal thuja. This protection will work both in winter and summer. The same applies to other conifers, but they are not so compact.
You can plant any plants that are suitable for a green fence. To quickly improve the situation, plant ivy or bindweed. They, at least for the summer, will make the site quieter.
New Technologies
In the Czech Republic, a new liquid coating has been developed to improve sound-absorbing characteristics. It’s made from recycled tires. It is a rubber crumb that can be painted with pigment. A binder is added to it, after which the mass is applied to the finished fence. The advantages are obvious: no alterations are needed, the mass of the fence does not increase too much, the “sail” does not increase. So far, this new product has not been found on sale.
But the idea itself is very similar to the material that has recently been actively promoted as a seamless rubber coating. It seems that you can apply it on a fence made of profiled sheet, on concrete or brick. It is unlikely to make friends with wood, but it is completely compatible with the listed materials.