How to map a noise? One approach would be to measure it using smartphone sensors. This would require development of an app and the community of users. Guys from real-estate website Trulia decided to map it based on already available data sources. They took data about location of noise complains in New York, Seattle, and San Francisco between 2010 and 2015 and visualized it on the map using CartoDB.
This data does have some limitations, as it only registers noise complaints made to police, and not actual decibel levels. That’s why places like Times Square doesn’t register as a noise hot spot, as there are no complaints. Still, it’s an interesting approach to mapping out the sounds of a city.