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Center for Advancing Research in Transportation Emissions, Energy, and Health (CARTEEH)

A USDOT University Transportation Center

Noise Barriers

Constructing noise barriers on highways and other high-traffic roadways can mitigate noise impacts from vehicles and construction equipment. This is a common noise reduction method that can either be man-made or vegetation barriers.1 Natural vegetation barriers can include hills, tree lines, or earth berms or mounds, and are used to maintain a natural appearance.2 Additionally, using sound absorptive wall treatments on barriers, bridges, or tunnels is another solution to further minimize noise exposure. In general, highway noise barriers should be tall enough to reduce noise levels for people living nearby, be visually appealing or preserve urban aesthetics, and not increase noise levels on the opposite side of the roadway.

Considering this strategy will help achieve the goal of the following objectives

  • Less Contamination
  • Less Emissions
  • Less Traffic Noise
  • Connectivity and Inclusion
  • Healthy Destinations
  • Less Traffic Violence
  • Active Transportation
  • Green Space

Transportation lifecycle phases

This strategy is associated with the following transportation lifecycle phases:

  • Construction
  • End of Life
  • Maintenance
  • Material Selection
  • Operations
  • Policy and Planning
  • Project Development

Who's involved

  • Construction companies
  • Local governments
  • Policymakers
  • Transit agencies
Constructing noise barriers on highways and other high-traffic roadways can mitigate noise impacts from vehicles and construction equipment. This is a common noise reduction method that can either be man-made or vegetation barrier.1 Natural vegetation barriers can include hills, tree lines, or earth berms or mounds, and are used to maintain a natural appearance.2 Additionally, using sound absorptive wall treatments on barriers, bridges, or tunnels is another solution to further minimize noise exposure. In general, highway noise barriers should be tall enough to reduce noise levels for people living nearby, be visually appealing or preserve urban aesthetics, and not increase noise levels on the opposite side of the roadway.

How it Helps

The establishment of noise screens is a measure to reduce the distribution of noise levels, rather than a source control measure.3 To protect the most vulnerable populations, noise barriers can be constructed between highways and locations with noise-sensitive populations such as schools, nursing homes, hospitals, or single-family homes.4

Implementing

Design:

To be effective, noise barriers should be constructed high enough to effectively block road noise from traveling a significant distance. Noise walls are generally between 12 and 18 feet high and constructed from brick, concrete, metal, wood, or other materials.4 However, noise barriers can vary widely in their design and construction material.5 For example, past noise barriers often consisted of simple reflective surfaces, but more modern barriers tend to have absorptive surfaces that serve to absorb some of the traffic noise.

Path of Sound:

Prior to constructing noise barriers, engineers should evaluate the many paths that sound can take when encountering a noise barrier.6 For example, noise can either bounce off the wall, be diffracted over the top, or even go through the barrier. Studies that assess the scattering of sound are important to determine how to design noise barriers.

Examples

1) Minnesota Department of Transportation (MnDOT) Standalone Noise Barrier Program

MnDOT’s Standalone Noise Barrier Program provides funding for the construction of noise barriers along Minnesota highways to reduce the public’s exposure to traffic noise. MnDOT keeps track of areas where residential noise standards are higher than recommended levels, and cities can submit an application about the area where a barrier is requested.

https://www.dot.state.mn.us/projectselection/lists/noise-barriers-metro.html

2) Sound Fighter Systems

Manufacturers such as Sound Fighter Systems provide different types of highway noise barriers for various applications. They offer sound-absorptive barriers that weigh less than traditional concrete barriers and reduce overall traffic noise levels.

https://www.soundfighter.com/applications/roads-and-highways/

1. Oeler Industries. Controlling Highway Noise. https://www.oeler.com/highway-noise/
2. Rochat, J., et al. (2020). Summary of Noise-Reducing Strategies. National Cooperative Highway Research Program. https://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP25-57TechMemo.pdf
3. The Danish Environmental Protection Agency. (2003). Proposal for a strategy to limit noise from road traffic. https://eng.mst.dk/media/mst/69033/Road%20traffic%20noise%20strategy%20UK%20version.pdf
4. AASHTO Center for Environmental Excellence. Traffic Noise & Transportation. https://environment.transportation.org/education/environmental-topics/traffic-noise/traffic-noise-overview/
5. Murphy, E., et al. (2014). Chapter 7—Noise Mitigation Approaches. Environmental Noise Pollution, 203-245. https://doi.org/10.1016/B978-0-12-411595-8.00007-0
6. Rochat, J. L. (2016). Highway Traffic Noise. Acoustics Today, 124, 38-47. https://acousticstoday.org/wp-content/uploads/2016/12/Highway-Noise.pdf