This map shows modeled outdoor noise across Trojan 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 2 Trojan residents, or 2.0%, live above that level. By land area, 2.6% of Trojan is above 55 dBA.
See how noise in Trojan compares to similar-sized cities.
Noise by Part of Trojan
Average noise levels for Trojan residents, grouped by direction from the center of Trojan. Southern Trojan carries the highest population-weighted average; Western Trojan carries the lowest. Just 1% of residents in Western Trojan live in blocks above the EPA's 55 dBA threshold, a third of the share in Southern Trojan.
Eastern Trojan
2% of people above 55 dBA
Northern Trojan
2% of people above 55 dBA
Southern Trojan
3% of people above 55 dBA
Western Trojan
1% of people above 55 dBA
Southern Trojan sounds about 58% louder than Western Trojan to the human ear, a 6.6 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 Spearfish Mtn BR 2E do you need to be?
Spearfish Mtn BR 2E produces an estimated 59 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 48% of Trojan sits under tree canopy (heavier than most cities) and roughly 0% 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.