Noise Barrier Design Handbook

Atmospheric Effects

Atmospheric Absorption, Refraction, Turbulence

Field measurements should not be performed when wind speeds are greater than 5 m/s, or when strong winds with small vector components exist in the direction of propagation.

3.3.1
14.1.2.1
15.1.2

Barrier Design Goals

Barrier Sound Transmission

Barrier panel materials should weigh 20 kg/m² or more for a transmission loss of at least 20 dB(A).

3.4.2

Barrier Length

Ensure barrier height and length are such that only a small portion of sound diffracts around the edges

3.5.2

Wall vs. Berm

A berm requires more surface area, but provides 1 to 3 dB(A) additional attenuation versus a wall.

3.5.3

Reflective vs. Absorptive

Communities may perceive sound level increases due to reflections. Sound reflected between parallel barriers may cause degradations in each barrier's performance from 2 to as much as 6 dB(A), but in most practical situations, the degradation is smaller.

3.5.4

Overlapping Barriers

Ensure the ratio between overlap distance and gap width (between barriers) is at least 4:1.

3.5.5.1

Special Tops for Barriers

The cost of constructing these special shapes typically outweigh the cost of simply increasing the barrier's height to accomplish the same acoustic benefit.

3.5.5.3

Noise Berm

Aesthetic

Consider the visual implications on both residential and highway side and the landscaping required.

4.1.1

Consider the destruction of existing features for construction of the berm.

4.1.1

Drainage and Utility

Provide for adequate drainage requirements.

4.1.1

Safety

Consider right-of-way requirements.

4.1.1

Maintenance

Consider accessibility to and around berm and landscaping requirements.

4.1.1

Post and Panel Noise Wall

Acoustical

Ensure that there are no sound transmission leaks between stacked panels and panel-to-post connections.

4.1.2,1

Aesthetic

Coordinate texture treatments with stacked panels so that the joints are either concealed by the pattern or become a part of the pattern.

4.1.2.1

Consider special concerns related to tilted post and panel designs.

4.1.2.1.1

Drainage and Utility

Overhead wires and other utilities may preclude the ability to use full height precast panels.

4.1.2.1

Structural

Provide for the impact of panel-to-post wind and dead load transfers.

4.1.2.1

Provide specialized loading treatments related to tilted post and panel designs.

4.1.2.1.1

Free Standing Noise Wall:
Precast Concrete

Maintenance

Consider landscaping access requirements.

4.1.2.3.1

Installation

For precast : consider size limitations, shipping requirements, traffic implications, reusability of precast panels, quality assurance process.

4.1.2.3.1
5.1

For cast-in-place: consider on-site material testing and inspection procedures during construction and on an as-erected product and weather concerns for on-site casting and curing.

4.1.2.6
5.1

Free Standing Noise Wall:
Planted or Bin-Type

Aesthetic

Consider the type of plantings.

4.1.2.3.2

Maintenance

Ensure landscaping upkeep.

4.1.2.3.2

Consider litter implications.

12.7

Safety

Consider implementing a deterrent for climbing on barrier girts.

4.1.2.3.2

Free Standing Noise Wall:
- Stone Crib

Safety

Consider implementing a deterrent for climbing on barrier girts.

4.1.2.3.3

Direct Burial Panels

Acoustical

Consider possible separating and gapping at the vertical tongue and groove joints.

4.1.2.4

Aesthetic

Consider a jagged top-of-wall profile rather than a smooth profile.

4.1.2.4

Structural

Consider possible differential settlement of panels.

4.1.2.4

Noise Walls Used to Partially Retain Earth

Structural

Consider loading concerns on the retained soil.

4.1.2.5

Consider the impact if adjacent land owners re-grade their property in the vicinity of the noise wall.

4.1.2.5

Drainage and Utility

Ensure proper drainage so that water does not "pond" or saturate the soil retained by the noise wall.

4.1.2.5

Cast-in-Place

Aesthetic

Form liners and architectural inserts must be placed on vertical surfaces of the form work which may increase imperfections in the wall surface.

4.1.2.6

Application of concrete retarding chemicals to the vertical form work surfaces for the purposes of obtaining an exposed aggregate finish is difficult.

4.1.2.6

Installation

Consider on-site material testing and inspection during construction and on an as-erected product.

4.1.2.6

Consider weather concerns for on-site casting and curing.

4.1.2.6

Combination Noise Wall and Noise Berm

Structural

Consider reactive loadings on the berm's soil due to the wall portion.

4.1.3

Consider a plateau area on top of the berm.

4.1.3

Safety

Consider the need for and location of right-of-way fence.

4.1.3

Noise Walls on Bridges

Structural

Consider weight stress and rotational loading.

4.2.1

Consider bridge vibrations due to existing traffic.

4.2.1

Consider bridge vibrations from construction operations.

4.2.1

Consider the impact of any parapet attachments.

4.2.1

Consider the type of anchoring system.

4.2.1

Consider top of barrier profile if the top of parapet profile is not smooth and/or consistent.

4.2.1

Safety

Ensure protection of traffic (both on and beneath bridge).

4.2.1.4

Consider the potential for damage and injury in the event of the noise wall or parts thereof falling from the structure.

4.2.1.5

Ensure adequate vehicular sight distance.

4.2.1.6

Consider barrier shading resulting in highway icing, and adverse effects on highway lighting.

4.2.1.6

Maintenance

Consider accessibility.

4.2.1.7

Consider snow drifting and storage implications.

4.2.1.7

Consider possible restrictions to bridge inspection teams.

4.2.1.7

Noise Walls on Retaining Walls

Structural

Consider any additional dead and torsion loads due to the noise wall.

4.2.2

Drainage and Utility

Provide for adequate drainage requirements.

4.2.2

Concrete

Aesthetic

For cast-in-place: form liners and architectural inserts must be placed on vertical surfaces of the form work which can increase the chance of imperfections in the wall surface.

5.1

For cast-in-place: application of concrete retarding chemicals to the vertical form work surfaces for the purposes of obtaining an exposed aggregate finish is difficult.

5.1

For cast-in-place: other surface textures obtained through raking, brushing, or stamping of concrete are not possible.

5.1

Surface textures:

• Smooth Surface - Ensure a smooth surface by performing a final "rubbing" of the concrete with a thin cement mixture.
• Exposed Aggregate - Provide sufficient screening, grading, and inspection to ensure the removal of any iron ore aggregate which could give the appearance of rust "bleeding" from the panel.
• Form Liners - The joints must be tight, adequately secured to the form work, and "lined up" in terms of the form liner pattern. Care must be taken to avoid jagged edges at the ends and sides of the panels.
• Inserts - Care must be taken to ensure an adequate bond/attachment between the insert and the noise barrier panel.
• Veneers - The primary consideration of the use of veneers is related to assuring an adequate attachment bond.
• Stucco - The cleanliness and roughness of the concrete noise barrier surface is critical in order to ensure an adequate bonding surface for the stucco.

5.9.1.1

Quality control and consistency is critical in the production of pigmented concrete since unevenness and blotchiness can become apparent, particularly on smooth surfaces. The maximum protection against the visual effects of damage can be provided by use of a pigmented panel with a surface stain of a matching color. The added cost of such a dual treatment may, however, not be warranted in many cases.

5.9.2.1
5.9.3

Drainage and Utility

Application of concrete retarding chemicals to the vertical form work surfaces for the purposes of obtaining an exposed aggregate finish is difficult.

5.1

Safety

Consider on-site material testing and inspection during construction.

5.1

Installation

For precast , consider size limitations, shipping requirements, traffic implications, reusability of precast panels, quality assurance process

4.1.2.3.1
5.1

For cast-in-place, consider on-site material testing and inspection procedures during construction, and weather concerns for on-site casting and curing.

4.1.2.6
5.1

Maintenance

For free-standing noise walls, consider access for landscaping.

4.1.2.6

Brick and Masonry Block

Aesthetic

Surface textures:

• Exposed Aggregate - Consider limited use due to mass production constraints.
• Form Liners - While some molds may be applied to the production of concrete blocks, their use is rare and limited.
• Veneers - Ensure an adequate attachment bond.
• Stucco - The cleanliness and roughness of the noise barrier surface is critical in order to ensure an adequate bonding surface for the stucco.

5.2
5.9.1.2

Quality control and consistency is critical in the production of pigmented blocks since unevenness and blotchiness can become apparent, particularly on smooth surfaces.

5.2
5.9.2.1
5.9.3

Structural

Consider the need for a continuous concrete foundation.

5.2
8.4

Consider the compressive strength of the concrete materials.

5.2

Installation

Hand-laid versus preassembled panels:

• Consider each type's versatility to conform to ground contours.
• Consider each type's speed of erection.
• Consider special leveling courses on grades of up to 6 percent.
• Consider the scaffolding requirements for hand-laid panels.

5.2
11.1

Metal

Acoustical

Consider the Sound Transmission Class requirements.

5.3

Aesthetic

Consider the possible "industrial" appearance of metal walls.

5.3

Consider weathering steel concerns because unpainted rusting panels can stain adjacent concrete.

5.3

Manufacturers' requirements (related to both coating and material coated) such as extent of sand blasting, cleaning materials, temperature and moisture controls, etc. need to be adhered to closely.

5.9.2.3
5.9.3

Structural

Consider the non-compatibility of various metal combinations.

5.3

Ensure corrosion resistance.

5.3

Consider the metal's structural strength.

5.3

Safety

Consider the possible glare due to on-coming vehicles.

5.3

Consider implementing a deterrent for climbing on barrier girts.

5.3

Maintenance

Debris and errant vehicles easily causes noticeable damage.

5.3

Wood

Acoustical

Consider possible shrinkage and warping causing noise leakage through gaps.

5.4

Ensure a tight fit for tongue and groove planking to avoid noise leakage.

5.4

Aesthetic

Selection of a wood species for its color attributes must also consider durability, warping, rot resistence, etc. The type of treatment, stain, or paint must be compatible with the type of wood, nails, etc. used in the barrier assembly, and with the environment in which the barrier will be placed. Chemical reactions between steel nails and wood preservative treatments may corrode nails. Moisture content at the time of paint or stain application is also critical.

5.9.2.4
5.9.3

Safety

Consider the wood's burning characteristics when choosing a wood.

5.4

Consideration should be given to a wood's shatter resistance.

5.4

Transparent Panels

Structural

Consider the various methods of mounting.

5.5

Consider edge conditioning the panels.

5.5

Safety

Consideration should be given to shatter resistance.

5.5

Consider the possible glare due to on-coming vehicles.

5.5

Maintenance

Consider the methods of cleaning the panels.

5.5

Consider the maintenance concerns related to vandalism and scratches.

5.5

Consider the need for ultraviolet light protection.

5.5

Debris and errant vehicles easily causes noticeable damage.

5.5

Cost

Transparent noise barriers costs can be more costly than common concrete or steel panels.

5.5

Plastics

Acoustical

Consider the possible shrinkage in plastic materials.

5.6

Safety

Consideration should be given to the material's shatter resistance.

5.6

Consider the possible glare due to on-coming vehicles.

5.6

Consider the burning characteristics of the materials.

5.6

Maintenance

Consider the need for ultraviolet light protection.

5.6

Consider the maintenance concerns related to vandalism and scratches.

5.6

Recycled Rubber

Acoustical

Consider possible coating interference with the material's Noise Reduction Coefficient.

5.7

Ensure an adequate Sound Transmission Class.

5.7

Recycled rubber material generally cannot be pigmented. Rubber can be coated (usually with a more expensive polyurethane coating) to obtain a desired color.

5.9.2.6
5.9.3

Structural

Consider the panel's structural strength requirements.

5.7

Consider the material's bonding requirements.

5.7

Safety

Consider the need for flame retardants.

5.7

Consider the material's possible toxicity concerns.

5.7

Composites

N/A

(Refer also to concerns for individual materials within composites) Particular concern must be paid to ensure compatibility between the barrier materials (including any glues, attaching devices, etc.) and the applied coating to negate any potential for damaging chemical reactions.

5.8
5.9.3

Alignment Changes

Acoustical

Shifts and transitions into the barrier's alignment must be made within the restrictions and tolerances of the barrier system components. Combined shifts in both horizontal and vertical alignment must avoid reflecting flanking sound waves back into the community.

6.1.1

Vertical Stepping/ Sloping of Panels

Aesthetic

To avoid having to cast non-rectangular panels, stepping of panels should be made at the location of the posts with consideration also given to sloping the post tops at a consistent angle.

6.1.2

Caps

Aesthetic

Consider the aesthetic concerns related to the size of the cap in proportion to the scale of the noise wall and related to the horizontal and vertical alignment of the cap with the entire barrier.

6.1.3

Drainage and Utility

Provide for adequate drainage requirements.

6.1.3

Structural

Attachment and caulking details need to be carefully considered at the panel-to-post attachment points and between cap sections.

6.1.3

Maintenance

Barriers with large horizontal caps may shade the top portion of a barrier and prevent the natural cleansing of that area by rain water.

6.1.3

Barrier Ends

Cost

When considering a barrier end treatment, the decision should weigh costs against any acoustical and/or aesthetic reasons.

6.1.4

View from the Road

.

Small detail elements and textures are less apparent from this perspective. The barrier is seen from low angle views, and its overall shape and patterns become more apparent. Also note the different perspective of drivers traveling in opposite directions.

6.1.6

View from Adjacent Land Uses

.

Because of the potential closeness of barriers, the relative height of the barrier in proportion to the distance from the receptor is a factor requiring consideration. Horizontal shifts and top of barrier steps, slopes and transitions property boundaries require planning to minimize adverse visual conditions.

6.1.7

Landscaping

Aesthetic

Trees, high scrubs, and vines could hide aesthetic inserts, designs cast in noise barriers, or other specifically designed aesthetic features of the noise barriers.

6.1.8

Drainage and Utility

Drainage under, along, or through the noise barrier could be affected by landscaping placed in inappropriate locations.

6.1.8

Safety

Plantings could restrict access through barrier overlap areas, to access doors or fire hose valves, or to the noise barrier itself. Plantings could also obscure the identification signs for these access features.

6.1.8

Litter

Landscaping in a high litter area should also consider what type of vegetation is best to use. A thorny type of bush may make litter cleanup more difficult than such litter removal from a grassy area.

12.7

Drainage

Barrier Overlap

Ensure the acoustical requirements of such overlaps are met

3.5.5.1
7.1.1

Accommodating Water Through a Barrier

Ensure that the size and location of openings do not result in degradation of acoustical performance, and also ensure protection in the form of grates or bars is provided to restrict entry by small animals.

7.1.2

Accommodating Water Under a Barrier

If a porous stone systems is used, maintenance is required to ensure it does not seal up over time with sediments.

7.1.3

Flood Plain Areas

Include possible design additions where the bottom panels of a precast concrete panel system can be hinged so that the pressure of any built-up water would swing the panels outward, allowing the release of flood waters.

7.1.4

Lighting, Sign Supports, Utility Poles, Etc.

.

When mounting traffic or safety-related elements on or adjacent to noise barriers, care needs to be taken to ensure that adequate horizontal and vertical clearances are provided.

7.2

Underground Utilities

.

Utilities in the path of a barrier can preclude the use of certain types of deep footings and require use of either a shallow spread footing or a barrier design which requires no footing. An undulating noise wall configuration may be used to "jog around" underground utilities.

7.3

Overhead Utilities

.

If vertical clearances are limited, stacked panels and smaller lifting equipment may be required - or the barrier type may be limited to a block wall or a cast-in-place wall.

7.4

Expansion and Contraction of Materials

Post to Panel Connections

Care must be taken to ensure that caulking and/or shimming material do not restrict panel expansion or contraction.

8.1

Panel to Panel Connections

Care must be taken to allow sufficient movement within panel to panel connections while maintaining tight joints.

8.1

Expansion Joints

Vertical expansion joints are required at sufficient intervals to preclude cracking in cast-in-place and brick/masonry barrier systems.

8.1

Ground- to Structure-Mounted Connections

Consideration must be given to connections between ground-mounted and structure-mounted barriers.

8.1

Structure-Mounted

For structure-mounted barriers, consideration must be given to the expansion/contraction at the structure's expansion joint locations.

8.1

Noise Barrier Loadings

Dead Load

Consider possible modifications to the structure design to accommodate barrier weight.

8.2

Consideration must be given to ice loads caused by water freezing and building up on exposed barrier surfaces.

8.2

Snow Load

Consider the need for area available for safe storage of plowed snow and the location of the barrier for snow clearing and removal equipment.

8.2

Barrier Height Limitations

Aesthetics

Because of the potential closeness of barriers, reduce the visual dominance of a very tall barrier by locating the barrier at least 2-4 times its height from the nearest receiver.

6.1.7
8.3

Drainage and Utility

Barrier height may be limited by the presence of overhead utilities.

7.4
8.3

Structural

Consideration must be given to foundation requirements of tall barriers.

8.3

Foundation Requirements

Earth vs. Rock

The following factors contribute to the selection of the type of footing to be used as well as their depth and size:

• The characteristics of the surrounding soil or rock;
• Possible ground movements;
• Anticipated future excavation activity adjacent to the foundations;
• Ground water levels;
• Extent of frost penetration;
• Extent of seasonal volume changes of cohesive soils;
• The proximity and depth of foundations of adjacent structures; and
• Overall ground stability, particularly adjacent to cut or fill slopes.

8.4

Concrete Footings in Earth

Concrete for drilled or augured footings should be cast entirely against undisturbed soil. The concrete should have an opportunity to cure properly before the noise panels are installed.

8.4.1

Concrete Footings in Rock

All excavations into rock should be backfilled entirely with concrete.

8.4.2

Qualitative Evaluation of Safety

Modifications to Barrier Design

Consider the safety implications of a barrier's location.

9.1.2

Reinforcement additions add weight to the barrier which can be a problem on structure-mounted barriers.

9.1.2

Consider the safety implications of a barrier's type.

9.1.2

Consider barrier protective devices as part of the overall barrier design.

9.1.2

Sight Distance

.

Sight distance concerns along horizontal curve sections of highways and at locations where a barrier terminates near a highway's or ramp's intersection with another roadway.

9.2

Emergency Access

Barrier Overlap

Ensure the acoustical requirements of such overlaps are met (see Table Item 9-1).

3.5.5.1
9.4.1

Ensure the safety of pedestrians within or near the gap.

9.4.1

Access Doors

Doors need to be designed so as to be acoustically "sealed" when closed. When not in use, doors should be locked to avoid unauthorized access.

9.4.2

Emergency Access for Utilities

Careful consideration must be given to the design of large utility access doors, which over time, have a tendency to warp due to their massive size.

9.4.2

Fire Safety

Hose Couplers

Ensure the correct size connection and ensure the capability of withstanding the thrust loads generated by the force of the moving water in the hose lines.

9.5

Panel Mounted Valves

Ensure the capability of withstanding thrust loads, and keep in mind that the closure caps and their retaining chains can become the target of theft and vandalism.

9.5

Small Covered Openings

A device is needed to seal the opening when it is not in use in order to avoid acoustic degradation and to restrict the passage of small animals.

9.5

.

Note that identification signs are required on both sides of the barrier to enable the proper coordination of emergency personnel.

9.5

Glare

Tilted Walls

Walls tilted for acoustical reasons may cause glare.

4.1.2.1.1
9.6

Anti-glare Screens

Dependent on the type of material used, the screen may alter the acoustical characteristics of the roadway.

9.6

Shatter Resistance

Barriers on Structure

Particular concern should be given for barriers on structure overpassing another highway causing potential injury to nearby vehicles, pedestrians.

9.7

Safety

Consideration should be given to the potential shatter resistance of transparent and plastic barrier materials.

4.2.1, 5.5,
5.6 & 9.7

Icing and Snow Removal

Structural

Ensure that the barrier can withstand the additional loads that may result from plowed snow being both thrown and piled up against the barrier

8.2
9.8

Maintenance

Place barriers a sufficient distance from the travel way to ensure adequate space for storage of plowed snow

9.8

Evaluation Process

Submission

It is critical to know what the requirements and specifications are for acceptance by the responsible organization. And, just as important, in what format are the agencies accustomed to seeing these submissions?

10.1.1

Detailed Evaluation

Some caution must be exercised in the acceptance of samples for testing to be certain that the samples truly represent the product to be furnished.

10.1.3

Performance Feedback

It is essential that a comprehensive regiment of conducting routine observations of service performance be established. It is also important to involve field staff by encouraging them to routinely check for early signs of problems, by instructing them on what to look for, and how to report it.

10.1.6

Sampling and Testing Requirements

.

The testing specimens used should be cut from a finished production run product as opposed to small handmade pieces that were specifically made for the test. By insisting on this, the test results can also be used to evaluate in-plant quality control and production operations.

10.3

Criteria for Approval

Acceptance of Design

If the vendor changes the design of the system or any of its components, then the system should be reevaluated.

10.4.1

Site Grading & Preparation

.

All graded earth should be compacted to reduce or eliminate settling of the surrounding earth and possibly creating gaps at the base of the wall between the panels and the ground line.

11.1

Quality Assurances

Testing Methods

Non-destructive testing is the preferred method; however, it may not always be the most accurate, or possible, for the determination and verification of some properties.

11.3

Construction Tolerances

.

Regardless of the aesthetic treatment and changes in elevation to accommodate alignment shifts, the minimum specified height of the noise barrier should be maintained at all times.

11.5.1

Installation Materials & Processes

Grout, Caulking, and Sealants

It is critical to ensure that light cannot be seen through any part of the noise barrier system and that the filler material or flashing does not trap water inside the wall components or near the base and foundation of the wall.

11.5.2

Coatings

If painted, stained or galvanized surfaces become abraded during shipping, storage, etc., those surfaces should be cleaned and re-coated.

11.5.5

Availability of Replacement Parts

.

If barrier components are custom made for a specific project, then the issue of replacement parts becomes very critical.

12.2

Access

.

If the only location to place an effective noise barrier is relatively inaccessible, then the design should focus on developing a barrier and related surface treatment and landscaping which is relatively maintenance free.

12.3

Surface/ Material Wear and Deterioration

Deterioration from Moisture

If the design may result in moisture ponding on its surface, consideration should be given to redesign replacement parts. In some climatic conditions, consideration should be given in the design phase to selecting a barrier and surface treatment which can minimize mildew and mold growth and be capable of being cleaned on a regular basis.

12.4

Deterioration from Ultraviolet Light Exposure

When using paints, stains, graffiti coatings, and stenciled designs, consideration should be given to the effects of ultraviolet light, especially in the design of transparent barriers.

12.4

Loss of Stains and Painted Coatings

If the coating or stain is providing protection for the barrier material, then it becomes an issue of reduced life expectancy of the material.

12.4

Landscaping

.

The issue of consistency between the barrier's aesthetic treatment, including landscaping, and the maintenance philosophy of the owner of the barrier is critical. Manpower and financial constraints may appropriately lead to the selection of vegetation that is native "maintenance free" and to a plan that will foster growth of natural vegetation.

12.5

Litter

.

Barrier design should consider the location of a noise barrier in terms of litter susceptibility, the barrier's ability to "trap" litter, and the philosophy of the responsible organization regarding cleanup of litter. Landscaping in a high litter area should also consider what type of vegetation is best to use. A thorny type of bush may make litter cleanup more difficult than such litter removal from a grassy area. Special design features such as insert areas, planter boxes, etc. may "catch" litter or even become target areas for litterers.

12.7

Snow

Storage

Consideration must given to a barrier's susceptibility to damage from snow ploughing operations by both the force of the snow being thrown against the barrier and the resultant pressure of the snow piled-up against the barrier.

12.8

Drifting

Consideration should be given to snow drifting in the design stage so that, in critical areas, the possibilities of wide shoulders and minimum necessary barrier heights can be incorporated.

12.9

Physical Conditions and Factors

Transportation of Material, Equipment, and Work Force

If barrier materials must be shipped from far-away distances, costs will be greater than for locally obtained material. If specialized expertise is needed for a particular barrier installation, the required man powers' proximity to the project will be a factor influencing cost.

13.2.2

Quantity of Barrier

The unit cost of a small quantity of a noise barrier will likely cost more than the unit cost for larger quantities of a barrier.

13.2.3

Material Availability

If materials must be specially ordered, or if long manufacturing lead time is required, construction schedules can be affected, adding costs to the barrier construction.

13.2.4

Traffic Protection and Detours

The cost of traffic protection/detours may increase barrier installation cost. The contractor may charge a higher unit cost for barrier construction performed close to traffic as compared to construction in a less restricted area.

13.2.6

Limitation of Construction Hours

Less efficient and more costly production can be expected when construction hours are limited or interrupted. Commitments made to communities to restrict either the hours of construction operations, the level of noise generated by such operations, or specific equipment used in the proximity of residential dwellings or other sensitive land uses will likely add cost to the noise barrier.

13.2.7