This map shows modeled outdoor noise across Alta Sierra 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 526 Alta Sierra residents, or 7.8%, live above that level. By land area, 9.4% of Alta Sierra is above 55 dBA.
See how noise in Alta Sierra compares to similar-sized cities.
Noise by Part of Alta Sierra
Average noise levels for Alta Sierra residents, grouped by direction from the center of Alta Sierra. Central Alta Sierra carries the highest population-weighted average; Southern Alta Sierra carries the lowest. Just 5% of residents in Southern Alta Sierra live in blocks above the EPA's 55 dBA threshold, about half the share in Central Alta Sierra.
Central Alta Sierra
11% of people above 55 dBA
Eastern Alta Sierra
6% of people above 55 dBA
Northern Alta Sierra
11% of people above 55 dBA
Southern Alta Sierra
5% of people above 55 dBA
Western Alta Sierra
6% of people above 55 dBA
Central Alta Sierra sounds about 31% louder than Southern Alta Sierra to the human ear, a 3.9 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.
How far back from do you need to be?
produces an estimated 70 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 soft rainfall.
Calculated from the model's calibrated attenuation formula. About 41% of Alta Sierra sits under tree canopy (heavier than most cities) and roughly 12% 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.