Green buffers for screening and noise reduction

GEORGIA FORESTRY COMMISSION

Green Buffers for Screening and Noise Reduction

Introduction Communities are developing more rapidly today than at any time in our history. Land is becoming more scarce, and developments more dense. As lot sizes shrink, we move closer to our neighbors - along with the sights and sounds they create. A higher level of urban sounds has come to be known as "noise pollution." Elevated sound levels impact our physical health, stress levels, and quality of life in much the same way that other, more obvious forms of pollution affect us. "Visual pollution" is much more difficult to quantify. One person's "trash" is another person's "art," and many people prefer to be screened from their neighbors' chosen landscape.

Beginning design tips for noise reduction:

This booklet discusses basic landscape tools and guidelines for optimizing sound reduction and visual screening. Keep in mind that distance, height, density of materials used, and cost considerations will determine what can reasonably be accomplished.
Impacting Noise Pollution Residents have achieved success with a number of methods that minimize noise pollution, including building walls, planting vegetation, and creating fountains that mask offensive sounds. Research shows it is more effective to use a multi-faceted approach to noise reduction rather than a single tool. Wellplanned efforts may reduce noise levels by as much as 50%.

n Maximize personal distance from the sound source. Most loud sounds will dissipate over extended distances.
n Use structures (walls and berms) and vegetation (grass, shrubs and trees) to break sound lines. Don't hesitate to use all resources at hand, particularly existing vegetation.
n Utilize and economize all space. A combination of distance, structures, and vegetation will provide the most benefit.
When trying to reduce noise levels it is important to absorb, deflect, and muffle intrusive sound as close to the source as possible. For most homeowners that point is the property line.
Opportunities and Materials Berms Earthen berms help absorb noise from low elevation sound sources. Construction should be at least 3 feet wide for every 1 foot in height, and planted with appropriate grasses or shrubs.
Walls Sound barrier walls reflect and deflect noise. They may be constructed of stone, concrete, wood or recycled structural materials. Denser materials create greater sound deflection and absorption. The closer the wall is to the sound source, the more the sound will

be reduced. Often, a short wall close to the source will provide the same impact as a much larger structure further away. A wall-height barrier that screens the source from view is usually sufficient. Each increased meter of wall height above the line of sight attenuates sound by as much as 1.5 db(A).
Vegetation Plant materials help attenuate sound and "calm" the noise. Some types of plants are better at performing this function than others. Efficient trees and shrubs have thick, waxy leaves, dense evergreen foliage, and branches that extend to the ground. Always be sure to properly install plant materials according to University of Georgia Extension Service or Georgia Forestry Commission guidelines.

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Procedures for Noise Screening 1. Determine the source of the noise
and the area to be screened. Heavy traffic noise will likely require a scheme similar to the detail shown below. This requires a minimum of dense shrubs, a solid wall (wood, stone, or recycled material), and two rows of evergreen trees.
2. Should traffic noise be of a lighter nature, a berm and shrubs may be sufficient. These tools should be placed as close to the sound source or curb as possible. On occasion, a simple, low wall and shrub planting will suffice.
3. Make sure the shrub planting is designed for individual plants to overlap and eventually touch as they grow large. This will provide an uninterrupted buffer of foliage.
4. Allow adequate space for the growth of the trees and shrubs, and don't crowd them too close together. An effective planting plan will screen more noise over time.
5. Tree plantings should be staged in two staggered rows (where space allows), to provide visual screening of the sound source.

Unshielded House

Shadow Zone

Shielded House Noise Barrier

Source: FHWA

Design note: Noise reduction in urban environments is a matter of "getting in the way" of the sound with the "right materials." A significant amount of the perceived sound attenuation is a function of the sound source being "out of sight." This may require different strategies for different types of situations (i.e. a second story window will require a different screen type than would a first floor patio). Remember, home surfaces (walls and cement) also reflect sound and may serve to accentuate noise problems if not screened.

6. A typical buffer for heavy noise reduction might appear as shown below. Note the integrated and overlapping plantings with each feature suited to the site.
Establishing Visual Screens Visual screening has become a more frequent challenge for homeowners. Established residents may disagree with new neighbors about what looks acceptable. New homeowners may find themselves "too close" to their

neighbors' windows. When mutual effort is put into the design and establishment of a screen, the desired effect has a greater chance of pleasing all homeowners. Visual screening may be easier and less expensive to achieve depending upon the level of screening desired (a 100% visual screen can be very expensive and difficult to achieve in a short period of time), if you follow a few basic principles.

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Procedure for Visual Screening The basic principles of visual screening are the same as those for buffering sound, except that visual screens may not need the same level of occlusion to achieve desired results.
1. Determine the length and height of the area to be screened. An elevated visual problem, such as a second story window, may require the use of a berm and taller trees to get the desired results.

2. Check to see how the view changes from different vantage points around your yard and home. Attempt to have the screening plan address all these views.
3. Usually, a simple multi-row planting of a combination of trees and shrubs will suffice. Make sure the shrub planting is designed for individual plants to overlap and eventually touch as they grows large.

4. Where only trees are used, plantings should be of two staggered rows (where space allows), to provide visual screening. Remember to allow for the growth of the trees and shrubs, and don't crowd them too close together.

There may be a need for a variety of vegetation/fence combinations to achieve the required level of screening.

Additionally, the screening of second story views may require larger growing materials and permanent structures employed
together to get the desired result over time.

Images Source: PALC, Bristish Columbia, Ca.

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Plant Materials for Urban Noise Reduction

Recommended Over story Trees

Scientific Name -

Common Name

~edru~ atlantica

Atlas Cedar

Cedrus deodara

Deodar Cedar

Cr~12tomeria ia12:Qnica -

Japanese Cryptomeria

Cunressus arizonica

Arizona Cypress

Cunninghamia lanceolata -

Common Chinafir

Cunressocxnaris le!lan dii

Leyland Cypress

JynillfET!d~ virginiflna-

Eastern Red Cedar

Milill21 ia vir~:-iciaoa-

Sweetbay MagnoIia

Magu2lia gmcslitl2m -
Meta~~uQia gl}!lltQ~ttQ2Qide~

Southern MagnoIia Dawn Redwood

Pinu~ ~trol;!us -

White pine

Pinus taeda-

Loblolly Pine

Pinus virginiana-

Virginia Pine

Thuja occidentalis

A rborvitae

R ecomme nded Understory Trees

Height 40-60

Spacing 30

40-60

30

50-70

40

30-40

20

50-70

30

60-70

15

40-60

25

I 5-25

20

60-80

50

70-1 00

40

60-80

40

60-80

25

40-60

25

40-60

15

Sun/Shade Drainage

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Scientific Name -
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II!:!X !<<!in!:! llex decidua llex x Nellie R. Stevens 11i!2!; X QQS!~ II!:!X VQmiiQri<! M~rica cerifera -
Recommended Shrubs
Scientific Name llex comuta "Carissa" flex comuta "Ro tunda" Ilex conluta "Dwarf Burford" llex vomitoria "Nana" Juniper chinensis "Pfitz.eriana" Loropetalum chinensis

Common Name Savannah Holly Dahoon Holly Decidious Holly Nellie R. Stevens Holly Ame rican Holly Yaupon Holly Waxmyrtle
Common Name Carrisa Holly Dwarf Chineese Dwarf Burford Dwarf Yaupon Pfitzer Juniper Chinese Loropetalum

Height 15-30 20-30 20-30 15-35 20-40 15-20 10-20

Spacing 15 15 15 15 15 10 15

Sun/Shade Drainage

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Height 3 - 4' 3- 4' 5 - 8' 3 -5' 5-6' 3-5'

Spacing 3' 3' 5' 4' 5' 8'

S un/Shade Drainage

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M yrica cerifera " pumil la9' Osmanthus x fortunci

DwarfWaxmyrtle Fortunes Osmanthus

3- 5'

5'

10- 15'

8'

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Resource Information Cook, D.I. and D.F. Van Haverbeke. 1977. Suburban Noise Control with Plant Materials and Solid Barriers. Research Bulletin EM-100 Rocky Mountain Research Station, USDA Forest Service, University of Nebraska, Lincoln, NE.
Dirr, Michael, Fourth Edition. 1990 Manual of Woody Landscape Plants. Stipes Publishing, Champaign, IL. 1007 p.

Highway Traffic Noise, 1992. A publication of the US Department of Transportation - Federal Highway Administration (www.fhwa.dot.gov).
Landscape Plants for Georgia; Bulletin # 625 University of Georgia Extension Service, Athens, Georgia.
Noise Mitigation Research and Vegetative Noise Barriers; I-25 Corridor Evaluation January 2002, Colorado Department of Transportation, Region 2, Pueblo, Colorado.

Permanent Agriculture Resources, 1998 Pub. #60 Trees as Noise Buffers, USDA, National Agroforestry Center. Lincoln, Nebraska.
Special thanks to Steve Brady - UGA/CES; Valerie Pickard - NRCS; and Larry Morris GFC for their additions and editing assistance.

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"Green Buffers for Screening and Noise Reduction" is a publication of the Sustainable Community Forestry Program of Georgia Forestry Commission.
2008
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GEO.Gil IOIUTU CO MM ISSIO N
P. 0. Box 819 Macon, GA 31202 1-800-GA-TREES GaTrees.org
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