This map shows modeled outdoor noise across Santa Clara 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 736,774 Santa Clara County residents, or 42.8%, live above that level. By land area, 43.9% of Santa Clara County is above 55 dBA.
See how noise in Santa Clara County compares to similar-sized counties.
Noise by Part of Santa Clara County
Average noise levels for Santa Clara County residents, grouped by direction from the center of Santa Clara County. Central Santa Clara County carries the highest population-weighted average; Southern Santa Clara County carries the lowest. Just 34% of residents in Southern Santa Clara County live in blocks above the EPA's 55 dBA threshold, a third of the share in Central Santa Clara County.
Central Santa Clara County
100% of people above 55 dBA
Eastern Santa Clara County
44% of people above 55 dBA
Northern Santa Clara County
54% of people above 55 dBA
Southern Santa Clara County
34% of people above 55 dBA
Western Santa Clara County
41% of people above 55 dBA
Central Santa Clara County sounds about 97% louder than Southern Santa Clara County to the human ear, a 9.8 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 Santa Clara 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-880 do you need to be?
I-880 produces an estimated 81 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 suburban street at night.
Calculated from the model's calibrated attenuation formula. About 8% of Santa Clara County sits under tree canopy (lighter than most counties) and roughly 54% 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 Santa Clara 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
Norman Y Mineta San Jose International (SJC) sits north of Santa Clara 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 90 dBA on the map's Overall layer. Blocks on the opposite side of Santa Clara County, particularly to the south, show no measurable aviation contribution. Use the Aviation toggle on the map above to isolate the airport's footprint.
How Noise Is Distributed Across Santa Clara County
The bar chart below shows the share of Santa Clara County residents in each noise band. About 55% of residents live below the EPA's 55 dBA threshold, and roughly 17% live in blocks above 60 dBA. Long-term exposure in that range is linked to elevated stress hormones and cardiovascular risk.
How Santa Clara County Compares
Santa Clara County sits at the quieter end of the spectrum. Below: how Santa Clara County's average outdoor noise and share of residents above the EPA threshold compare with Alameda County, San Mateo County, Contra Costa County, and San Francisco County.
Average noise level (dBA)
Santa Clara County's 55.2 dBA pop-weighted average is at the quieter end of the spectrum. California as a whole averages 54.0 dBA and the U.S. averages 52.0 dBA. Both are lower than Santa Clara County because most of either area is rural land away from major roads.
Share of residents above 55 dBA
About 42.8% of Santa Clara 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, 43.9% of Santa Clara County's footprint sits above 55 dBA, against a California average of 36.0% and a national average of 28.1%.
What This Means if You're Moving to Santa Clara 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-880 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 8% of Santa Clara County is under tree cover (lighter than most counties), and the dominant land cover is medium-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. Norman Y Mineta San Jose International's approach paths concentrate aviation noise to the north. Neighborhoods to the south 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.