This map shows modeled outdoor noise across Redwood City 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 32,104 Redwood City residents, or 40.4%, live above that level. By land area, 41.7% of Redwood City is above 55 dBA.
See how noise in Redwood City compares to similar-sized cities.
Noise by Part of Redwood City
Average noise levels for Redwood City residents, grouped by direction from the center of Redwood City. Eastern Redwood City carries the highest population-weighted average; Western Redwood City carries the lowest. Just 27% of residents in Western Redwood City live in blocks above the EPA's 55 dBA threshold, about half the share in Eastern Redwood City.
Central Redwood City
55% of people above 55 dBA
Eastern Redwood City
60% of people above 55 dBA
Northern Redwood City
36% of people above 55 dBA
Southern Redwood City
37% of people above 55 dBA
Western Redwood City
27% of people above 55 dBA
Eastern Redwood City sounds about 48% louder than Western Redwood City to the human ear, a 5.7 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 Redwood City 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 US Hwy 101 do you need to be?
US Hwy 101 produces an estimated 79 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 13% of Redwood City sits under tree canopy (lighter than most cities) and roughly 56% 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 Redwood City. 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
San Francisco International (SFO) sits northwest of Redwood City. The U.S. Department of Transportation measures aviation noise around this airport directly, 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 45 dBA on the map's Overall layer. Blocks on the opposite side of Redwood City, particularly to the southeast, show no measurable aviation contribution. Use the Aviation toggle on the map above to isolate the airport's footprint.
How Noise Is Distributed Across Redwood City
The bar chart below shows the share of Redwood City residents in each noise band. About 62% of residents live below the EPA's 55 dBA threshold, and roughly 9% live in blocks above 60 dBA. Long-term exposure in that range is linked to elevated stress hormones and cardiovascular risk.
How Redwood City Compares
Redwood City sits the lowest among the peer group. Below: how Redwood City's average outdoor noise and share of residents above the EPA threshold compare with San Mateo, Mountain View, Palo Alto, and San Leandro.
Average noise level (dBA)
Redwood City's 53.9 dBA pop-weighted average is the lowest among the peer group. California as a whole averages 54.0 dBA and the U.S. averages 52.0 dBA. Both are lower than Redwood City because most of either area is rural land away from major roads.
Share of residents above 55 dBA
About 40.4% of Redwood City residents live in blocks where outdoor levels exceed the EPA's 55 dBA threshold. That's fewer than any of its peer group. Measured by land area instead, 41.7% of Redwood City'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 Redwood City
- 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 US Hwy 101 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 13% of Redwood City is under tree cover (lighter than most cities), 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. San Francisco International's approach paths concentrate aviation noise to the northwest. Neighborhoods to the southeast 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.