Ink,
Like I said if it's electrical you'll see it at the panel,blown fuze or poppped circuit. If it's structural you may never find it,a joist can crack along the grain and make a tremendous noise but show very little visual damage.BTW this is common in older homes that use real lumber!
My home was built in the 40's real 2x4's not these 1 and a half by 3 and a half junk they use today! The wood is so old and dry you can hardly pry a nail from it and the house creaks all the time. Ya and my wife thinks we have ghost's too,she can hear them walking around,I tend to beleive it's the wood shrinking or expanding with the season changes.
If you heat in the winter it will dry the wood,then shut off heat and the moisture is absorbed and the wood expands and make a hellava noise.
Another thing that can cause a loud bang is gas or water lines,though not as common it's been known to happen,ever heard pipes knock when you shut a tap or open it? It's the reason they use bumper pipes around clotheswashers and water heaters.
Of course YMMV.
