How to reduce noise in your backyard

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It’s a sunny Saturday afternoon, and you’re lounging in your backyard deckchair. You’ve been looking forward to this moment of peace all week; a time when you can unwind after days of hard work and appreciate the simple pleasures of life – some quiet tranquillity in the your lush botanical setting. You take a deep breath in, but suddenly find your moment of peace disturbed by the beeping of car horns, whining noises stemming from a faulty water pump and dogs barking in the neighbouring property. You scramble to your feet, exasperated and frustrated that you can’t seem to have just 20 minutes of quiet in your garden.

A number of city dwellers experience such frustration and stress as a result of noise intrusions, often on a daily basis. Indeed, a 2003 study by Brown and Bullen found that up to 20% of dwellings in Australian cities (excluding Canberra and Brisbane – lucky you!) were exposed to traffic noise well above the recommended World Health Organisation, and this percentage is likely to have increased in recent years given Australia’s expanding population and the recent building boom. A noisy environment has been found to increase the risk of hearing loss, generalised anxiety disorder, and can even reduce life span.

Fortunately, a variety of solutions exist to resolve such issue, or at the very least, reduce the impact of intrusive noises. Before investigating the ways in which noise interferences can be reduced, let’s take a look at how exactly sound minimisation operates in a backyard…

Get the basics right

First, consider what you are trying to achieve: sound attenuation or sound deflection? While sound deflection is the most effective way to “kill sound” by bouncing unwanted sound waves against a barrier back to the source, it is also a lot harder (and expensive!) to achieve. Sound attenuation is a more common solution that consists in lowering the intensity of the sound by absorbing sound waves.

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Other criteria are to be considered when designing your solution:

  • Height: Make your sound barrier as high as possible to prevent noise from rolling over the top of the barrier. As a general recommendation, a wall barrier will need to be about two metres high to sufficiently block out noise from a nearby road. The key message to remember is that blocking the line of sight will help to block the line of sound. However, most local councils will have regulations for such matter, so be sure to check the height and width restrictions before embarking on your building project.
  • Density and Rigidity: Ideally, create a high and long barrier with few spaces for sound to flow through. The type of environment and needs should also determine the density of your barrier – living close to a highway where rattling trailers whoosh past at 100km/h will call for a denser and more rigid barrier, but in a residential street with less frequent, but nonetheless annoying noises, a lower or smaller barrier may suffice.
  • Full Coverage: A noise barrier should also extend all the way to the ground. Gaps at the base will allow the skidding of cars, beeping of horns, rattling of washing machines or other such extraneous noises to enter underneath. Noise can also hit your backyard at angles, so it is advisable to stretch your barrier around corners and across as many sides of your garden as possible.
  • Proximity to the Sound: Sound protection barriers should be constructed as close to the noise source as possible (such as near the neighbouring property or near traffic). Alternatively, place the noise barrier close to a spot where you frequently sit, such as near an outdoor table.

Wall of greenery

One of the first and most economical solutions to consider is a simple wall of dense shrubbery: as well as being aesthetically appealing, trees naturally absorb sound in an effective way. Additionally, the rustling of leaves can operate as white noise, reducing the impact of minor sounds from the lawnmower or trimmer in the adjacent property.

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A green barrier needs to meet certain requirements to effectively block out sharper and louder noises. Ideally sitting close to the source of noise, or near areas that are frequented, such as a backyard deckchair, the barrier should also wrap completely around the space you want to soundproof to ensure maximum sound protection. Planting should be at least 7.5–9 metres thick and very dense – sound waves can creep through the tiniest of openings.

The best sorts of trees to plant are those with thick branches and trunks that can reflect and absorb sound waves. At least one row of tall evergreen trees, followed by an inner row of evergreen shrubs will ensure that your dense green barrier spans all seasons.

Dense vegetation tends to create psychological benefits for residents too – viewing greenery can help to reduce levels of stress that may be caused by the extraneous noises from outside. However, if you live in a particularly noisy area, a more impermeable barrier, such as a wall or fence may be necessary to block out very loud noises. Indeed, even with very dense rows of greenery, a green barrier will result in only about a 25% noise reduction.

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Alternatively you can combine greenery with a wall or fence to get the best of both worlds. Natural landscapes create visual interest and help to soften the harsh lines of a solid wall. As an alternative, a stepping fence can also break up the repetitive monotony of man-made barriers.

Straw, brushwood or hay bales

It may sound like something out of the fairy tale, ‘The Three Little Pigs’, but straw or hay bales can serve as excellent noise proof barriers. Interior sounds often seem louder in an enclosed straw bale space, since internal sounds are not drowned out by external noises.

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If you are after a more permanent noise barrier, consider lining your hay or straw bale with cement to create a smooth exterior, often indistinguishable from masonry.

Screen walls

In some instances, household owners may wish to erect a screen instead of a long solid wall or fence. A screen is a shorter and smaller version of a fence, cement or brick wall. Thus the effectiveness and cost of your screen will depend on the type of material used.

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External screens are more economical and suitable than an a proper wall if only a small outdoor seated area requires noise protection. Screens are often built closer to a seated area, rather than along the boundary line, since they are designed to block out noise for a particular area close to the sound recipient, like a deck.

Screens can be a very cost-effective solution if your needs in term of noise reduction are limited and you simply don’t have the time or space to grow a tree line.

Fences

Fences usually come in two kinds: timber and metal.

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Timber fences are a cost-effective solution, but with a relatively short shelf life, susceptible to fire and can rot easily if not treated properly. Timber should therefore be used sparingly, and never in bushfire prone zones. Easy to install, timber fences are simply not strong enough to withstand strong winds and tend to naturally fall apart easily with time, forcing numerous repairs and replacements upon the owner.

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For maximum result, a timber fence should have no visible gaps. If there is even a small gap between timber slats, the effect of your fence will diminish. One solution would be to seal openings in wooden fences with an additional layer of timber. The diagram below shows two methods of constructing a solid timber fence, both of which will help to ensure that small gaps are sufficiently covered.

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Sturdier, a metal fence such as Colorbond is a more durable fencing alternative to timber. Still prone to fly off with the wind, they tend to last long enough to be a good investment. However, in term of aesthetics, this is as far as will get: nothing screams “cheap” more than metal fences, so homeowners looking for a grand entrance, beware.

Fences are likely to be less effective in blocking out noise than a sturdy wall. Fences often have tiny cracks, through which sound waves will be able to creep through. In addition, they tend to be thinner than a more traditional wall, so sound can more easily flow into your garden.

Soundproofing qualities of fences can be enhanced with the addition of noise reducing materials. Padded material converts sound waves into mechanical movement and friction, absorbing the sound rather than letting it pass through to your peaceful garden setting. Highly durable and able to withstand exposure to dirt, grass, storms and oil, sound bloc king fencing is an economical way of combating issues of privacy and noise in the backyard.

Walls as sound protection

In general, a dense wall made of solid or composite barrier placed between the source of noise and receiver is typically the best solution to reduce the effects of intrusive noises.

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Due to their sheer mass and weight, brick has excellent sound-reducing properties, provided there are no weak components. Most dense walls can provide up to a 50% reduction in noise. Even if the wall is at a lower height than you would ideally like, the mass of a dense concrete wall will help to deaden the sound of traffic and other intrusive noises. As a highly durable material, concrete walls can provide a long-lasting solution to your backyard noise problem.

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However, traditional materials like brick or cement tend to be a very expensive option. For those with a more limited budget, a more cost-effective alternative to brick walls are modular walls: with an overall cost of only half the price of a regular brick wall, you can make some real savings without impacting on the quality and sound reduction properties.

Ideal for higher walls and tight spaces in the garden, modular walls can suit most backyard environments.

In addition, modular walls only take 1/5th of the time to install. A real time-saver for customers installing their fence as a weekend project.

Landscape design

Beyond the simple choice of material used for your noise barrier, a well-designed backyard can help a long way to prevent noise intrusions from arising. For example, building a deck on the opposite side of the home, as far away from the road as possible, is one such way to reduce noise intrusions.

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Another great option is to dig a garden oasis that would sit on a lower level than the rest of your property. The soil surrounding your nestled oasis can function as an acoustic barrier, using retaining walls to hold up the soil and quieten incoming noises.

Additions to noise barriers

Over the years, homeowners have developed other unusual solutions to minimise sound disturbance, with great creativity.

Water Features

This simple solution to noise intrusions has been used for centuries – for example, fountains were often placed in the centre point of courtyards during medieval times, or in serene Japanese gardens to fade out noises from the surrounding bustling city.

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Today, water fountains can be used in conjunction with a noise protection barrier to block out intrusive noises. The continuous pleasant sound of trickling water will help to overpower the unpleasant intrusive noises for two primary reasons. First, the pleasant sounds operate at the same frequency as many extraneous invasive noises, such as lawn mowers and air conditioners. Secondly, the water sounds will be in closer proximity to you than the street, so they are likely to flood out roadside traffic. It is best to place your water feature close to a spot where you frequently sit – such as near an outdoor seated area, or next to a backyard deckchair. Alternatively, construct the water feature or other barrier close to the source of noise. For example, if traffic is your main concern, place the fountain right close to the road.

Water features can be as elaborate or minimalistic as you like. From an expensive, ornamental sprouting fountain, to a simple stone birdbath or copper tub fitted with a recirculation pump, water will help to cultivate a calmer and quieter environment. If choosing a fountain, select one that makes loud splashes, particularly during the busiest times of day when the traffic is bothersome. You can turn most recirculation pumps down to a softer level during quieter hours.

However, bear in mind that fountains probably won’t flood out noises at a vastly different frequency, such as horns or alarms. For optimal noise protection, pair the fountain with an additional barrier.

Other ‘White Noise’

But water features are not the only name in the game: you can introduce other pleasant sounds into the garden to counteract intrusive noises. For example, certain native trees, such as Eucalyptus species, banksias and wattles, tend to attract birds and other wildlife. The tweeting and chirping of birds will be music to your ears compared to the persistent lawnmower grind or washing machine rattle next door.

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Wind chimes can also produce a distinctive and soothing sound.

“Psycho-acoustics”

This emerging field of study explores how visual stimuli can alter our perception of intrusive noises. Roger Cook, landscape contractor at This Old House providing expert advice on home improvement, remodelling, gardening and decorating, contends that greenery “that blocks the view of the noise’s source will always make a property more comfortable… Even a nice lawn will make you feel farther from the road”[i]. The barrier itself may not directly reduce the decibels of sound, but you will perceive your garden as a more peaceful and noise-free sanctuary.

Your own noise solution

So when it comes to minimise noise disturbance, there are more than one option, and often, the choice will lie within your budget restrictions and personal needs.

Also consider professional help: landscape or acoustic engineers are trained to find the best acoustic solution for any type of environment, and can recommend you the most suitable solution for your needs.

With a sound solution in place, soon you may forget you are even residing in a bustling city district. Barriers and other features will create a soothing oasis of backyard bliss. Savour the solitude, peace and privacy that such a setting provides, and delight in the joy of entertaining guests without noise disruptions.

Written by Sophie Deutsch

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