An applied mathematician and former Caltech teacher has mapped the loudness of every address in Los Angeles and is, naturally, releasing it in website form. HowLoud founder Brendan Farrell came up with an elaborate model that takes a sound profile of a site (based on stuff like vehicle flow, flight patterns, and nearby attractions), then uses "physics to propagate the noise through the environment" to determine how loud the area really is. The results also incorporate the time of day of the noise and the intensity ("a low-flying jet is worse than a light steady hum"). The site itself assigns a score to each location—the lower, the louder. HowLoud has shared two maps here colored by the relative noisiness around LA: one shows the average score for each neighborhood and one gloriously heatmaps the entire region.
HowLoud has mapped Los Angeles and Orange County, and plans to add estimates soon for specific sides and floors of big buildings. Meanwhile, they've just launched a Kickstarter today to expand the map to all of the US and Canada and refine their data a bit (separating heavy trucks out from regular vehicle traffic, for instance).
Searches on HowLoud are free; Farrell hopes to sell personal and business licenses eventually, meaning scores could end up on real estate listing sites.