Boxer Tummies!
Sancha makes all sorts of strange tummy noises. Her tummy growels louder than mine!! Sometimes, she farts so loudly that she startles herself!!
Maybe your pup is eating/drinking too quickly and is taking in excess air while gulping down his food. How many times do you feed him during the day? If you are only feeding once a day, you might want to try breaking up his meals and feeding two or three times throughout the day. When I started feeding Sancha three times/day I noticed that she held her food down better, had less gas (she's still a little farter!!), and her stools even seemed a little more firm.
Boxers also have pretty sensitive tummies, so I've found that it also helps to feed a little snack before bed time. They are such babies!