Living near a busy road comes with a range of problems, not least the noise level. If you’re looking for a natural way to reduce noise pollution, you might have wondered how to block road noise with trees. Well here’s a quick answer:
The most effective way to block road noise with trees is to use the densest ones possible. Trees or shrubs with dense foliage are able to dampen and reflect a portion of road noise, particularly higher frequencies. Combine with fences for best effect.
In this article, I’ll look at why trees are effective at blocking road noise, and will offer some tips for how to get the most out of a tree barrier.
Why are trees good at blocking noise?
Reducing noise works on the two basic principles of absorption and reflection. Some soundproofing products only do one, while others combine the two.
For example, something like mass loaded vinyl deflects sound waves, while acoustic foam both absorbs and reflects sound waves to reduce echo. Understanding these principles is key to effective noise reduction solutions.
Essentially, trees reduce noise pollution because they can both deflect and absorb sound waves. It’s similar to how acoustic foam works.
Acoustic foam has an open-celled structure that sound waves hit and bounce off in all different directions. They’re unable to leave again because of all the surfaces, and so their amplification is reduced.
Well, the same is true for trees. Their leaves or foliage basically act like thousands of small, oddly angled surfaces that sound waves can bounce off. As this happens, the sound waves lose energy and eventually dissipate.
Also, trees have quite a lot of mass, which is ideal for deflecting sound waves. Sound waves travel through objects by making them vibrate. The more mass the object has, the harder it is to vibrate. This means sound waves don’t travel as far.
While trees won’t completely block road noise, they can reduce it by up to 10dB. This might not sound like much, but it can seem like a 50% reduction in overall noise levels. When you live near a busy road, this can be more than enough.
In fact, several studies have been published on the noise reducing effects of tree barriers. Some of the most notable include Leonard and Parr (1970), Cook and Van Haverbeke (1972), and Huddart (1990).
These studies had varying results, but all found that planting a belt of trees up to 30m wide could reduce noise levels by 50% or more. While you might not be able to plant a 30m belt of trees, even a simple hedge will make a difference.
Another thing worth considering is that trees make their own noise. Many people find the sound of wind rustling through leaves to be very pleasant and calming, so this is something of a double bonus.
Rustling leaves will help to mask the sound of traffic coming from the road while the trees deflect a portion of the noise pollution. Combining these two elements will make noise reduction seem even more effective.
Which trees are best for noise blocking?
Of course, in order to get the most out of planting a noise-blocking tree barrier, you need to be selective with the type of trees you use. Here are some tips for choosing the right ones:
- Evergreen trees are best because they retain their foliage all year round, meaning you always have the benefits.
- You need trees with the densest foliage possible for best results.
- Choose species that grow quickly so you can have the benefits as soon as possible.
- Shrubs might be better than trees because they have foliage all the way to the base.
So what plants are best for noise blocking barriers?
- Cyprus trees
- Western red cedar
All of these species are ideal for this purpose because they’re evergreen, have dense foliage, and are fast growing. That said, you can’t expect full maturity in less than 5 years, but usually a decade.
Combining various types of trees and shrubs will give you the best results. For example, you could use a species of conifer for its thick, evergreen foliage along with a broadleaf evergreen, such as a laurel.
Doing this will give more effective sound reflection because there are different surfaces for the sound waves to bounce off. Much like how you have acoustic foam and bass traps for different frequencies, this is the same kind of idea.
Tips for reducing road noise with trees
Once you’ve selected the species you think will be best for your needs, it’s time to get planting. But in order to get the most out of this process, you’ll need to do a few things first.
- Cultivate the ground long before planting. Digging in some rotted manure will not only boost plant growth, but soft earth is a more effective sound absorber.
- Consider planting your trees on a berm. A berm is a mound of earth, and this will be an effective part of the noise-blocking barrier.
- Plant the trees in as wide a belt as possible. The wider it is, the more sound you’ll block.
- Establish your planting site as close to the noise source as possible. The closer it is, the more effective it’ll be.
Another thing to consider is adding in several different layers of trees and shrubs for maximum noise blocking. Noise blocking ability peaks at about 30ft for trees, after which they lose density in their lower branches.
To avoid this issue, plant a few rows of trees and shrubs. For example, have a row of juniper closest to the noise source, with a row of deciduous trees such as birch behind it. Then have a row of ornamental shrubs closest to your house for decoration.
If you do decide to plant the trees on a berm, it should be around 4ft high and 20ft wide with a flat top. Having sides with a 10% slope is most effective for blocking noise too. This might sound like a lot, but it’ll make a big difference – up to 15dB.
Maximizing Noise Blocking
While trees or shrubs will make a difference in the amount of noise pollution you hear in your home, they might not be enough on their own. This will obviously depend on how noisy the road is, and how quiet you want it to be.
Bear in mind, too, that trees take time to grow. If you buy mature specimens you’ll notice the effect immediately, but these are a more expensive option. Also, you’ll still have to plant them with room to grow, meaning there’ll be gaps in your hedge initially.
Luckily there are a few ways you can maximize the effectiveness of a tree barrier that keeps their aesthetic value but improves their noise-blocking ability.
First, consider building a wall. This might seem like it makes the trees redundant, but trees can grow taller than you’d build a wall. The benefit is that this offers immediate benefits and long-term protection.
A stone wall is best for blocking noise, but brick is effective too. Wood is the least effective, but would still make a difference.
You could always try building your own fence with soundproofing products like mass loaded vinyl (Amazon link). Vinyl fences are already a thing, as they’re hard-wearing and inexpensive. But obviously, they’re not very nice to look at.
With a bit of careful planting, you could hide the fence inside the row of trees or shrubs and it would end up completely hidden once they grow. This will arguably be the most effective way to block road noise using trees.
The benefit of adding a wall or other solid surface is that it’ll help to block lower frequency sound waves. Trees are more effective at higher frequencies, so this will help to solve this issue.
If you only need to make a small additional difference, consider options for masking noise. But these will only be worthwhile if it’s a small amount of noise you need to block.
You can’t expect to mask the sound of a freeway with these options.
- The first (and most effective) is to install a fountain. Flowing water is perfect for this kind of thing and will easily mask the sound of cars driving near your property.
- You could also consider installing some garden speakers so you can listen to music when outside. Many look like natural garden features and are weatherproof.
The drawback of these options is that they don’t block noise, but just try to cover it up. Also, it’s unlikely you’ll be playing music in your garden when you’re inside, so you might not benefit from them all the time.
Some Final Thoughts
Trees are a natural and effective way to block road noise coming into your property. I’ve found that you do have to be patient with this plan though, as trees take a long time to grow.
But with some careful planning, you can expect noise reduction of up to 50% just by using some trees. Hopefully, these tips will help you to have a more peaceful time in your yard.