Brian Barton
Trees are an effective natural solution to noise pollution, which is defined by the EPA as unwanted or disturbing sound. They act as sound barriers, reducing noise through a phenomenon called sound attenuation, which is the damping of sound. Trees attenuate noise by absorption, deflection, refraction, and masking. Noise absorption occurs when different parts of a tree, such as stems, leaves, branches, and wood, absorb sound waves. A noise barrier made of trees should be planted as close to the source of noise as possible to maximize its effectiveness. The width of the tree barrier is also important, with wider barriers providing greater noise reduction. The species of tree is another factor to consider, with broadleaf trees being the most effective at deflecting sound, and evergreens providing year-round noise reduction.
| Characteristics | Values |
|---|---|
| Noise reduction technique | Absorption, deflection, refraction, and masking |
| Noise reduction by | Trees, shrubs, bushes, vines, herbaceous plants |
| Noise reduction in decibels | 5-15 dB |
| Tree type | Hard-leaved, broadleaf, evergreen, coniferous, deciduous |
| Tree height | Up to 10-12m |
| Tree placement | Closer to the source of noise, in dense belts or wide strips |
| Additional measures | Soft ground surfaces, well-rotted organic matter in the soil |
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What You'll Learn
Trees act as noise barriers
Trees are an effective way to block noise. When strategically placed by a roadway, in a backyard, or in a park, trees help reduce unwanted noise. A 100-foot-wide tree barrier, for instance, can reduce noise by 5 to 8 decibels (dBA). The noise reduction is also closely related to the density of stems, branches, and leaves.
Broadleaf trees are most effective at deflecting sound. However, when broadleaf trees shed their leaves in winter, the sound barrier is lost. Evergreen trees, on the other hand, provide a consistent buffer against sound because they retain their needles or leaves across seasons. They also grow fast and can be planted close together, creating a denser barrier.
The selection and arrangement of trees are key to successfully blocking noise. Wide belts of high-density trees and shrubs are required to achieve significant noise reductions. For year-round noise reduction, use broadleaved evergreens or a combination of coniferous and broadleaved evergreen species. The effectiveness of noise reduction is also influenced by tree height, with noise reduction increasing with height up to 10-12 meters, after which it tends to decrease due to lower branches dying and allowing sound to travel more easily.
Trees can also be selected for the sounds they make in response to the wind or the animals they attract. Species with thick or papery leaves, like oaks, rustle in even a small breeze. The presence of vegetation can also attract wildlife, such as songbirds and crickets, that make pleasant sounds.
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Trees reduce noise through sound attenuation
Trees are a natural and effective way to reduce noise pollution through sound attenuation. Sound attenuation is the damping of sound through various means, including absorption, deflection, refraction, and masking. Trees are particularly good at absorbing sound, with their leaves, branches, stems, and wood acting as natural sound absorbers.
The effectiveness of trees in reducing noise pollution depends on several factors, including the species of tree, the density of the foliage, and the width of the tree barrier. Broadleaf trees, for example, are effective at deflecting sound, while evergreen trees provide a consistent buffer as they retain their needles or leaves across seasons. The width of the tree barrier is also important, with wider belts of trees providing greater noise reduction. Research has shown that a dense belt of trees and shrubs between 15-30 meters wide can reduce sound levels by 6-8 dB.
To maximize the noise-reducing effects of trees, it is important to strategically place them as close to the source of the noise as possible. This could include planting trees along roadways, in backyards, or in parks to create a natural sound barrier. The selection of the right tree species is also crucial, as some trees may be more effective at absorbing or deflecting sound than others. Online tools like the Arbor Day Foundation's Tree Wizard can help choose the appropriate species for a specific area.
In addition to their sound-absorbing properties, trees can also help reduce noise pollution through masking. Masking involves creating more pleasant sounds, such as the rustling of leaves in the wind or the attraction of wildlife, that offset unwanted noise. By carefully selecting tree species with thick or papery leaves, such as quaking aspen or oaks, the pleasant sound of rustling leaves can be maximized. The presence of vegetation can also attract wildlife, such as songbirds and crickets, that contribute to the masking effect with their pleasant sounds.
By utilizing the sound attenuation and masking properties of trees, urban areas can effectively reduce noise pollution and create a more pleasant and healthy acoustic environment for residents. The use of trees as natural sound barriers is an important strategy in noise abatement and can help mitigate the detrimental effects of noise on human health and well-being.
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Trees can be strategically placed to reduce noise
Evergreen trees provide a consistent buffer against sound because they keep their needles or leaves across seasons. They are also fast-growing and can be planted close together, creating a denser vegetation barrier. When choosing plants and trees for a sound barrier, it is important to select vegetation that will thrive in the local environment. Online tools like the Arbor Day Foundation’s Tree Wizard can help choose species appropriate for a specific area. Plants selected for noise walls also need to be tolerant of air pollution if they are going to be adjacent to roadways. A diversity of tree species, with a range of foliage shapes and sizes within the noise buffer, may also improve noise reduction. Foliage of the plants should persist from the ground up. A combination of shrubs and trees may be necessary to achieve this effect.
When possible, use tall plants. Where the use of tall trees is restricted, use combinations of shorter shrubs and tall grass or similar soft ground cover as opposed to harder paved surfaces. Noise reduction is closely related to the density of stems, branches, and leaves. For year-round noise reduction, use broadleaved evergreens or a combination of coniferous and broadleaved evergreen species. Soft ground is an efficient noise absorber. Cultivating the ground before planting and the addition of well-rotted organic matter to the soil surface may also help reduce noise while vegetation becomes established. Research also suggests that wide plantings (around 30 meters) of tall, dense trees combined with soft ground surfaces can reduce apparent loudness by at least 50%.
Trees can also be selected for the sounds they make in response to the wind or for the animals they will attract. Species with thick or papery leaves, like quaking aspen or oaks, rustle in even a small breeze. Bamboo is another option for a white noise-generating plant—however, non-native bamboo species can quickly spread out of control. The presence of vegetation can also attract wildlife, such as songbirds and crickets, that make pleasant sounds and allow one to feel more fully immersed in nature. The best noise barriers have diverse structures that prevent gaps and add varied textures to the environment. So, in addition to trees, effective sound barriers will include shrubs, bushes, vines, and herbaceous plants.
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The type of tree impacts noise reduction
The effectiveness of trees in reducing noise pollution depends on several factors, including the species, density, and height of the trees, as well as their placement relative to the noise source.
Broadleaf trees like oaks, maples, and beeches are excellent at diffusing noise due to their large leaves, which create a large surface area to break up sound waves. Their dense canopies also help to scatter sound waves, reducing their intensity before they reach inhabited areas. Additionally, the rustling of their leaves produces white noise, which helps to mask unpleasant urban sounds.
Evergreen trees, such as conifers (pines, spruces, and cedars), provide year-round noise reduction as they retain their foliage throughout the year. They are particularly effective in reducing high-frequency sounds, making them a popular choice for urban green buffers.
Fast-growing trees like hybrid poplars and willows can quickly establish dense sound barriers, making them ideal for rapidly urbanizing areas. While they may require more maintenance, their ability to create a noise-reducing buffer in a short period is highly valuable.
The unique characteristics of each tree species, such as dense foliage, height, and bark texture, contribute to their effectiveness in reducing noise pollution through sound absorption, deflection, and refraction. Trees with deeply grooved bark, such as oaks and pines, are particularly efficient in dispersing sound waves.
When strategically placed, trees act as natural noise barriers, providing an environmentally friendly solution to unwanted noise pollution.
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Urban greenspace helps reduce noise pollution
Urban greenspace is an effective way to reduce noise pollution in cities, which can have a detrimental impact on the health and wellbeing of residents. Noise pollution is defined by the EPA as "unwanted or disturbing sound", and can cause anxiety, tension, and even illness. Urban trees and plants can act as sound barriers, reducing noise levels by absorbing, deflecting, refracting, or masking sound waves.
Trees and plants are a natural way to combat noise pollution, and are particularly effective when strategically placed near roadways or in parks. A variety of tree species, with differing foliage shapes and sizes, can improve noise reduction. Tall trees are generally more effective at reducing noise, up to a height of around 10-12 meters, after which the lower branches tend to die off and allow sound to travel more easily. Evergreen trees, such as coniferous and broad-leaved species, are effective year-round as they retain their leaves or needles across the seasons. Broadleaf trees are also good at deflecting sound, although they lose their sound-reducing properties in the winter when they drop their leaves.
The density of the tree barrier is also important, with wider strips of vegetation resulting in greater noise reduction. A combination of trees and shrubs is often used, and soft ground surfaces can further enhance the noise-reducing effect. The species of tree and planting design must be carefully chosen, and trees should be planted as close to the source of the noise as possible. A 100-foot-wide tree barrier, for example, can reduce noise by 5 to 8 decibels, and even by 10 decibels in certain circumstances.
In addition to their sound-absorbing qualities, trees can also create more pleasant sounds in response to the wind, and can attract wildlife such as songbirds and crickets, further masking unwanted noise. Urban greenspace not only reduces noise pollution but also provides a host of other benefits, including improved air and water quality, recreational opportunities, and enhanced landscapes.
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Frequently asked questions
Trees act as noise barriers and reduce noise pollution through a phenomenon called sound attenuation, which is the damping of sound. Trees can absorb, deflect, refract, and mask sound waves.
A tactically designed 100-foot-wide tree barrier can reduce noise by 5 to 8 decibels. According to another source, a 100-foot-wide tree buffer planted 100 feet from a road can block about 10 decibels more noise than if it were planted 200 feet away.
Broadleaf trees are most effective at deflecting sound. However, they lose their leaves in winter, so the sound barrier is lost. Evergreen trees are a better option as they provide a consistent buffer against sound. They also grow quickly and can be planted close together to create a denser barrier.
Trees should be planted as close to the source of noise as possible. Wide belts of high-density trees and shrubs are required to achieve significant noise reductions.
Trees can also improve health and well-being, enhance air and water quality, and help with flood management.
