This map shows modeled outdoor noise across Merrimac 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 2,232 Merrimac residents, or 38.9%, live above that level. By land area, 44.4% of Merrimac is above 55 dBA.
See how noise in Merrimac compares to similar-sized cities.
Noise by Part of Merrimac
Average noise levels for Merrimac residents, grouped by direction from the center of Merrimac. The highest population-weighted average is in eastern Merrimac; the lowest is in western Merrimac, where just 7% of residents live in blocks above the EPA's 55 dBA threshold, a fifth of the share in the loudest section.
Eastern Merrimac
44% of people above 55 dBA
Southeastern Merrimac
51% of people above 55 dBA
Southwestern Merrimac
17% of people above 55 dBA
Northern Merrimac
7% of people above 55 dBA
Western Merrimac
7% of people above 55 dBA
To the human ear, noise in eastern Merrimac sounds about 251% louder than in western Merrimac, a 18.1 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 I-495 do you need to be?
I-495 produces an estimated 76 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 62% of Merrimac 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.