How NoiseLevelCheck Reads the Federal Noise Map

One federal source, not a survey

Every reading here comes from the US DOT Bureau of Transportation Statistics' National Transportation Noise Map (part of the National Transportation Atlas Database), which models road (2023 input data), rail and aviation (2022 input data) noise separately, then combines them into one 24-hour average sound level per point on the map.

Why this reads a map instead of querying an address

BTS's own point-lookup service for this map does not work: every hosted copy publishes with querying disabled, and the raw downloadable files return 403 to automated requests. What does work is the map's own image tiles, so NoiseLevelCheck reads the exact pixel color at each place's coordinates and matches it against the map's own published seven-band legend, the same classification a person would get reading the map by eye.

Caveat one: a 24-hour average, not HUD's day-night average

BTS reports LAeq, a straight 24-hour average. HUD and FAA's own noise standards are written in Ldn (day-night average level), which adds a 10 dB penalty to nighttime noise before averaging. A place with heavy overnight rail or truck traffic would score higher on Ldn than it does here; a place that's only loud in daytime would score about the same either way. So this site's HUD-zone reading is a conservative, disclosed approximation, not an exact Ldn classification.

Caveat two: some readings are honestly a range

BTS only publishes seven coarse bands, not a continuous number, and two of them straddle one of HUD's own dividing lines. Chicago, IL falls in the 60-69.9 dB(A) band, which straddles HUD's 65 dB(A) acceptable line, so its true zone could honestly be either side depending on where in that range the real value sits. Rather than picking one and hiding the uncertainty, that place's page says so directly.

What a full reading looks like

Baltimore, MD shows a complete example: a combined reading, a breakdown by road, rail and aviation, and a national rank, all traceable back to this same method.

Where to go next

Real examples: Chicago, IL, Baltimore, MD, New York, NY.

What HUD's Noise Zones Actually Mean · What Actually Cuts Road, Rail and Aircraft Noise