Street noise isn't generally a category-one issue for city governments, and they don't put a lot of resources into measuring it. The most they'll do is a set up temporary sound-level meters at certain locations, then generalize the readings over wider areas.
The method is not only relatively expensive, it doesn't even produce particularly detailed results, says Jesse Zaman, a researcher at the Free University of Brussels in Belgium.
Could citizens do a better job? The challenge, after all, isn't technological. Everything needed to record and map street noise is on a smartphone. The problem is distribution: Getting the sensors to enough places, so you can start building a map.
NoiseTube, an app and website developed in France and Belgium, gives a sense of what's possible. Allowing users to record and map noise in their neighborhood, it shows how citizen networks (like this one started in Spain) could complement government-run efforts, or perhaps replace them.
"By turning mobile phones into environmental sensors, we eliminate the need for expensive measuring equipment," Zaman says.
So far, 2,700 users have registered to participate at the NoiseTube site, with up to 10,000 people downloading the app (both Android and iOS). There are online and offline modes. In online, you just open the app and forget about it. It automatically uploads sound level data as you wander about. In offline mode, it stores the data on the phone, and you have to upload it later.
In either case, though, you can annotate as you go, tagging streets with descriptions and comments. That means you can make a time-stamped record of particularly noisy spots, in case you want to complain or convince.
Campaign groups in Belgium and Romania have used the maps to fight cases for noise reduction measures. But Zaman hopes to improve the flexibility of the system further, so groups can specify their own campaigns and derive data more easily. "The framework will automatically orchestrate these campaigns to ensure they result in qualitative data," he says.
More broadly, NoiseTube shows the potential for cheap sensors and apps to broaden environmental sensing in cities, especially around under-acknowledged problems like noise pollution, which don't generally get a lot of resources.