This map shows modeled outdoor noise across Polk 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 192,582 Polk County residents, or 42.4%, live above that level. By land area, 47.0% of Polk County is above 55 dBA.
See how noise in Polk County compares to similar-sized counties.
Noise by Part of Polk County
Average noise levels for Polk County residents, grouped by direction from the center of Polk County. Southern Polk County carries the highest population-weighted average; Central Polk County carries the lowest. Just 7% of residents in Central Polk County live in blocks above the EPA's 55 dBA threshold, a fifth of the share in Southern Polk County.
Central Polk County
7% of people above 55 dBA
Eastern Polk County
33% of people above 55 dBA
Northern Polk County
31% of people above 55 dBA
Southern Polk County
57% of people above 55 dBA
Western Polk County
44% of people above 55 dBA
Southern Polk County sounds about 39% louder than Central Polk County to the human ear, a 4.7 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 Polk 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-80 E do you need to be?
I-80 E produces an estimated 84 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 18% of Polk County sits under tree canopy (about average for counties) and roughly 34% 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 Polk 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.
Airport Noise
Des Moines International (DSM) sits south of Polk County. The U.S. Department of Transportation models aviation noise around this airport from federal traffic data, and the model uses those federal measurements rather than synthetic predictions.
Blocks under the approach and departure paths carry combined road-plus-aviation noise, with some exceeding 85 dBA on the map's Overall layer. Blocks on the opposite side of Polk County, particularly to the north, show no measurable aviation contribution. Use the Aviation toggle on the map above to isolate the airport's footprint.
How Noise Is Distributed Across Polk County
The bar chart below shows the share of Polk County residents in each noise band. About 47% of residents live below the EPA's 55 dBA threshold, and roughly 18% live in blocks above 60 dBA. Long-term exposure in that range is linked to elevated stress hormones and cardiovascular risk.
How Polk County Compares
Polk County sits the highest among the peer group. Below: how Polk County's average outdoor noise and share of residents above the EPA threshold compare with Dallas County, Story County, Warren County, and Jasper County.
Average noise level (dBA)
Polk County's 55.6 dBA pop-weighted average is the highest among the peer group. Iowa as a whole averages 52.2 dBA and the U.S. averages 52.0 dBA. Both are lower than Polk County because most of either area is rural land away from major roads.
Share of residents above 55 dBA
About 42.4% of Polk County residents live in blocks where outdoor levels exceed the EPA's 55 dBA threshold. That's more than any of its peer group. Measured by land area instead, 47.0% of Polk County's footprint sits above 55 dBA, against a Iowa average of 23.6% and a national average of 28.1%.
What This Means if You're Moving to Polk 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-80 E 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 18% of Polk County is under tree cover (about average for counties), and the dominant land cover is low-intensity developed land. 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.
- Airport noise is directional. Des Moines International's approach paths concentrate aviation noise to the south. Neighborhoods to the north of downtown show no measurable contribution from the airport.
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.