Noise Reduction Hedges is a controversial topic. There is no argument, though, that noise is one of the curses of modern life. So, can hedges really help?
The answer is yes, though perhaps not so much in the way you imagine. The reality is that sound can make its way through pretty much anything other than a vacuum. Yes, a forest will block out a motorway but a hedge can only do so much. Nevertheless, the difference a hedge can make, really can make a difference. Let’s start by looking at the simple steps you can take and at the impact planting the right kind of hedge can make…
Hedges and Noise Reduction – Which Varieties?
The most important thing is to choose an evergreen variety which has thick, dense foliage that grows all the way to ground level. You should also select a variety that is quick growing and buy the tallest plants your budget will allow. Taxus Baccata (Yew), Buxus Sempervirens (Box) and Ligustrum Vulgare (Privet) are all good choices. Many swear by Thuja Plicata Atrovirens (Western Red Cedar).
Leylandii might appear to be an obvious choice, but it is not as effective as the varieties just mentioned. Of course, several rows of Leylandii planted closely at the back of a large garden backing onto a motorway will help matters. However, if you are in that position, you will probably use the Leylandii as much to hide your high-tech sound-deadening acoustic fencing than to block the noise itself.
Basic Planting of Noise Reduction Hedges
Plant the hedge as close as possible to the source of the noise. Let it grow as tall as you can manage, ensuring it will not inconvenience your neighbour. In any case, talk to your neighbour – they may agree to a slightly taller hedge if they will also benefit from noise protection. Plant closer together – say seven plants per metre rather than five. Once mature, there should be no gaps.
Advanced Planting of Noise Reduction Hedges
In front of the main hedge (see previous post), plant shrubs with thick foliage growing from the ground up. Their ultimate height should be roughly half that of the hedge’s. Finally, under-plant the shrubs with thick, medium height perennials that are happy in the shade.
Remember, noise gets in as much from the bottom as it does over the top. Having two or more stages or layers helps because sound does not travel efficiently through changing densities.
Noise Reduction Hedge – Extreme Measures
The ultimate example of a Noise Reduction Hedge is the berm. A berm is essentially a raised bank of earth around 1.5m high and sloped with a ratio of 1:10. This is then heavily planted. The hedge is planted along its ridge. Berm’s are generally used on large landscaping projects as they should really be around 6-7m wide, but a scaled-down version could be useful to cut down noise coming in through the bottom. Acoustically, a berm (or similar) is a useful addition because they absorb low frequency noise like passing traffic.
By contrast, a hedge absorbs high frequency noise, generally the type we find most irritating. One other way a Noise Reduction Hedge work is more psychological than physical, though no less important or effective. Our brains are easily fooled. First, if it sees a barrier it automatically assumes that it is holding back whatever it is we are trying to hold back. Second, the brain thinks that a green, planted garden is less noisy and certainly calmer than one designed with man-made materials, particularly concrete, steel and even glass.
PS: Hedges and Noise Reduction – Aircraft
Sorry. If you are under the flight path of planes landing and taking off, no hedge, no fence will protect you in the garden. There is no triple-glazing for gardens that works against noise coming from the skies. However, as discussed above, a green garden will lessen the perceived impact of invasive Jumbos far better than a brown and grey one.