Popping noises. Could it be a pile driver somewhere? Any new buildings or bridges going in nearby? Also they could be airport noises if it's east
Also if you are close to the river check to see if there is some kind of project on the river itself. Bank stabilization or something like that. New
Or possibly the power plant has work going on?
edit on 30-9-2012 by ntech because: (no reason given)