I wouldn't be at all surprised to learn that the kid with the recording isn't pulling an April 1 "Ferris Buehler" synth trick on the townfolk...
OTOH, a couple of microbarograph arrays (like used to detect and triangulate on aboveground nuke tests) would be fairly cheap and easy to implement. Using off-the-shelf tubing, sensors, computers, I/O modules and software, and with the help of a good surveyor for precise siting, you could have mB arrays running in a week or two.