:shock: He's thumping that much? Is he in or outdoors? If outdoors, there may be a predator about that he has spotted or sensed, or perhaps sees a shadow that is making him uncomfortable.
If he's inside I would have to say your neighbors have amazing ears.. You could perhaps give him an extra handful of hay or grass, something to sooth and quiet him a bit, perhaps a little extra veg to settle him, but not enough to upset his diet.