This map shows modeled outdoor noise across St. Clair County at 100-meter resolution, combining road, aviation, and rail sources. Green areas measure below 45 dBA. Orange and red exceed the EPA's 55 dBA outdoor threshold linked to long-term health effects. Use the layer toggles to view each source on its own or all together.
What the numbers sound like
- 30 dBAWhisper
- 40 dBASoft rainfall
- 45 dBAQuiet suburban street at night
- 50 dBAQuiet office
- 55 dBAEPA outdoor threshold: light traffic 100 ft away
- 60 dBANormal conversation an arm's length away
- 65 dBABusy restaurant
- 70 dBAHighway traffic 50 ft away
- 80 dBACity bus interior
Population Above the EPA Outdoor Threshold
The EPA's 55 dBA outdoor reference level is a common benchmark for residential noise exposure, especially for activity interference, annoyance, and long-term community noise concerns. About 9,917 St. Clair County residents, or 11.4%, live above that level. By land area, 18.1% of St. Clair County is above 55 dBA.
See how noise in St. Clair County compares to similar-sized counties.
Noise by Part of St. Clair County
Average noise levels for St. Clair County residents, grouped by direction from the center of St. Clair County. Western St. Clair County carries the highest population-weighted average; Northern St. Clair County carries the lowest. Just 8% of residents in Northern St. Clair County live in blocks above the EPA's 55 dBA threshold, about two-thirds of the share in Western St. Clair County.
Eastern St. Clair County
14% of people above 55 dBA
Northern St. Clair County
8% of people above 55 dBA
Southern St. Clair County
11% of people above 55 dBA
Western St. Clair County
12% of people above 55 dBA
Western St. Clair County sounds about 19% louder than Northern St. Clair County to the human ear, a 2.5 dBA gap. Every 10 dBA roughly doubles perceived loudness. Within any of these directions, two homes a quarter mile apart can still differ by 10 or more dBA depending on how close they sit to a major highway.
Loudest Road Corridors
The model evaluates every road in St. Clair County using federal traffic counts, posted speeds, heavy-truck ratios, and pavement type. The source level shown is the modeled noise at the road centerline, where it is loudest. Noise drops with distance, faster in vegetated areas and slower over open pavement.
How far back from I-20 do you need to be?
I-20 produces an estimated 77 dBA at its loudest centerline points. Noise drops logarithmically with distance, with the exact rate depending on what's between you and the road. Tree cover, walls, terrain, and pavement type all matter. At roughly a quarter mile back, traffic fades into the noise level of a quiet office.
Calculated from the model's calibrated attenuation formula. About 50% of St. Clair County sits under tree canopy (much heavier than most counties) and roughly 10% is impervious surface like pavement and rooftops. Both are folded into the per-place decay rate above. Heavier canopy pulls noise down faster with distance; impervious surfaces slow the drop.
Rail Noise
Active freight rail runs through parts of St. Clair County. For most blocks the rail-only contribution is small. Combined road-plus-rail noise rarely exceeds road noise on its own. The exceptions are the handful of blocks within roughly a quarter mile of the right-of-way during pass-through hours.
Use the Rail toggle on the map above to isolate rail's contribution from road and aviation.
How Noise Is Distributed Across St. Clair County
The bar chart below shows the share of St. Clair County residents in each noise band. About 89% of residents live below the EPA's 55 dBA threshold, and roughly 5% live in blocks above 60 dBA. Long-term exposure in that range is linked to elevated stress hormones and cardiovascular risk.
How St. Clair County Compares
St. Clair County sits at the quieter end of the spectrum. Below: how St. Clair County's average outdoor noise and share of residents above the EPA threshold compare with Talladega County, Etowah County, Blount County, and Calhoun County.
Average noise level (dBA)
St. Clair County's 48.0 dBA pop-weighted average is at the quieter end of the spectrum. Alabama as a whole averages 49.0 dBA and the U.S. averages 52.0 dBA. Both are lower than St. Clair County because most of either area is rural land away from major roads.
Share of residents above 55 dBA
About 11.4% of St. Clair County residents live in blocks where outdoor levels exceed the EPA's 55 dBA threshold. That's in the middle of its peer group. Measured by land area instead, 18.1% of St. Clair County's footprint sits above 55 dBA, against a Alabama average of 20.0% and a national average of 28.1%.
What This Means if You're Moving to St. Clair County
- Distance from highways matters more than the neighborhood name. Two homes in the same zip code can differ by 20 dBA if one sits 100 meters from I-20 and the other 500 meters away. The model captures this at 100-meter resolution, so noise exposure changes block by block.
- Tree canopy can help reduce modeled noise exposure. Roughly 50% of St. Clair County is under tree cover (much heavier than most counties), and the dominant land cover is deciduous forest. Both are measured from federal USDA Forest Service and USGS satellite imagery at 30-meter resolution. Streets with 60% or higher canopy show 3 to 5 dBA lower noise than comparable streets with bare ground or pavement, which is why the per-place decay rate above already accounts for it.
Sources & Methodology
The BestNeighborhood noise model is calibrated against nearly one million federal ground-truth measurements across four states. Road noise is computed from segment-level federal traffic data and propagated outward using physics-based acoustic decay, with attenuation rates that depend on the surrounding land cover.
Federal datasets used:
FHWA Highway Performance Monitoring System: road geometry, traffic counts, lane configuration
U.S. DoT Bureau of Transportation Statistics National Transportation Noise Map: aviation and rail noise, road calibration ground truth
USGS / MRLC National Land Cover Database: land cover and impervious surface coverage
USDA Forest Service Tree Canopy Cover: vegetation density for sound propagation
U.S. Census Bureau TIGER/Line: block-level geography and population
U.S. EPA Levels Document: 55 dBA outdoor reference level
All inputs are published federal datasets. Block-level noise is computed by combining road, rail, and aviation sound sources in the energy domain, the same physics used in professional environmental noise assessments. Read the full methodology.