I have some noisy neighbours and I've thought of the same idea for controlling noise in neighbourhoods. You could have a microphone on every lamp post and send people fines for violating the rules.
I've been having a nightmarish time trying to track down intermittent low frequency industrial noise.
It's over the EPA regulations, it's neighborhood wide, and it is on for 2 hours between 11pm and 1am on random days. The EPA did monitoring of the house and site but couldn't pinpoint where it was coming from because of how low frequency it was.
This isn't surveillance, this is the equivalent of finding who is dumping raw sewage in your drinking water.
For 20Hz noise, are there too many reflections to use an oscilloscope with 3 mics on a 25ft baseline to triangulate it (you'd have to elevate the mics)?
Buy a whole load of the same model voice recorder, label them with tape for location, spread them out and record till batteries die, pull data to PC, repeat until get a sample? Someone above mentioned microsecond accurate clocks on raspberry pi being used for TDOA.
If there are any uniquely identify able patterns such that you found find that point on all microphones then deployment my sbts-aru project in four places surrounding it might very well localize it for you
