Noise Walls
Guided by community feedback, THEA is adding noise walls in residential areas within the project limits of the South Selmon Capacity Project. Noise walls are designed to reduce expressway noise and complement neighborhood aesthetics. Noise walls will be installed upon completion of construction on the additional lanes.
What is a noise wall?
A noise wall is a barrier built to absorb or reflect sound generated by expressway traffic. THEA constructs noise walls where expressway noise is projected to reach a level that significantly impacts a neighboring residence or other noise-sensitive property. While noise walls can meaningfully reduce sound levels, they do not eliminate all expressway noise.
Noise walls will be installed throughout residential areas along the 4.5-mile corridor and will feature an attractive brick design that complements the surrounding neighborhoods.
Wall heights by location
Noise Wall Artistic Concept
Heights vary based on each location’s noise analysis and engineering requirements (Roll Plots).
- 8 ft – Select mainline locations
- 14 ft – Select mainline locations
- 22 ft – Willow Ave off-ramp (ground-mounted)
The tallest wall – 22 feet – is a ground-mounted barrier at the Willow Avenue off-ramp. All other locations will have 8- or 14-foot walls based on individual site conditions.
How Noise Wall Locations Are Determined
THEA conducts a traffic noise analysis, as outlined in Title 23, Part 772 of Federal Regulations, during the planning phase of the project to evaluate noise levels and determine where abatement measures are warranted.
- Identify noise-sensitive areas: Residences, schools, churches, parks, and other properties that would benefit from lower noise levels are mapped within the project corridor.
- Determine traffic noise impacts: A noise wall is considered where projected noise levels will exceed 66 dB(A), or will increase by 15 dB(A) or more over existing conditions. Future traffic volumes are also factored in.
- Evaluate feasibility and reasonableness: To be considered reasonable, a wall must achieve a minimum noise reduction of 5 dB(A). Feasibility weighs cost, community input, aesthetics, land use, and engineering constraints.
- Determine installation: Walls are installed only where the analysis finds them both feasible and reasonable. Future traffic noise is accounted for upfront, so no re-evaluation is needed after construction.
Frequently Asked Questions
Q: Why are noise walls being installed after the lane widening is complete, rather than at the start of construction?
A: We understand the wait is frustrating, and we want to explain why this sequencing is necessary.
The noise walls are positioned at the outer edge of the expressway, in close proximity to where construction crews and heavy equipment will be working throughout the construction of the added inside lanes. The active construction zone along the project corridor is a tightly constrained space. Installing the noise walls first would place permanent structures directly in the path of ongoing construction activity, creating significant safety risks for workers and commuters.
By completing the added lanes first, crews will then have the space and access they need to safely operate. This is standard practice for highway expansion projects of this type.
Noise walls were included in the project specifically because of what residents told us mattered most to them.
Q: What are the noise walls made of, and will they look attractive?
A: The noise walls will feature an attractive brick design. Artistic renderings show what they may look like both from the expressway and from street level. The design was selected to be functional while complementing the character of the surrounding neighborhoods.
Q: How tall will the noise walls be?
A: Heights vary by location. Walls will be 8, 14, or 22 feet depending on where they are installed. The ground-mounted noise wall at the Willow Avenue off-ramp will be the tallest at 22 feet. All other walls will be 8 or 14 feet based on site-specific noise analysis.
Q: How were noise wall locations determined? Why doesn't my street have one?
A: Noise walls are installed in residential areas within the project limits based on traffic noise analysis and proximity to the expressway. Locations must meet state and federal criteria for feasibility and noise reduction effectiveness. If you have questions about a specific location, please contact the project team.
Q. Why aren't noise walls installed on the bridges?
A: Noise barriers mounted on elevated structures face stricter engineering and structural constraints than ground-mounted walls, and are limited to a maximum height of 8 feet. In some locations along the corridor, the elevated roadway geometry means a barrier of that height cannot achieve the minimum 5 dB(A) noise reduction required to be considered effective — even for residents living close to the expressway. If you have questions about a specific bridge location, please contact the project team.
Q: Will the noise walls block my view or sunlight?
A: Noise wall placement and height are engineered based on noise impact areas. THEA has worked to design them to be functional and aesthetically pleasing. If you have specific concerns, we encourage you to share that feedback with the project team.
Q: How much noise reduction do the walls provide?
A: Noise walls can reduce sound levels by as much as 50% for residents living very close to the expressway. The farther you are from the expressway, the less impact a wall may have. Walls in this project are designed to achieve a minimum reduction of 5 dB(A) where installed.
Q: Why doesn't my area qualify for a noise wall, even though I live near the expressway?
A: Several factors can affect whether a noise wall is warranted at a specific location, even for properties that appear close to the expressway.
- Distance and line-of-sight: Most impacted residences are within 200 feet of the expressway with a direct line-of-sight to the roadway. Properties set farther back, or shielded by buildings, hotels, or other structures between them and the expressway, may experience lower noise levels than expected.
- Elevated roadway geometry: Where the expressway is elevated, the roadway itself can act as a partial barrier for properties below it — particularly single-story homes. Multistory residences at the same elevation as the roadway may still be impacted.
- Structural height limits: Noise barriers mounted on elevated structures are capped at 8 feet. In some locations, this height is not sufficient to achieve the required 5 dB(A) reduction, meaning a wall would not provide a meaningful benefit even where noise levels are elevated.
- Shielding from nearby structures: Large adjacent buildings can block expressway noise from reaching properties behind them, resulting in noise levels that do not meet the 66 dB(A) threshold even for nearby residents.
If your property does not qualify, there are still steps you can take. Dense hedges, shrubs, and trees can absorb and deflect noise. Planting them close together with dense foliage improves their effectiveness. Combining vegetation with a tall fence offers the greatest noise reduction for private properties.