Why does my tummy growl?
Your stomach and guts squeeze in waves to move food along. When they are mostly empty, gas and liquid slosh around inside. The squeezing pushes that gas, and it makes a rumbly noise. The noise is louder when your tummy is empty, because there is less food to muffle it.
Transcript
Dr. Nina Byte: Chip asked me why his tummy growls. I am a doctor three times over, and this is what my life is now.
Dr. Nina Byte: Step one. Your stomach and guts squeeze in waves to move food along, like a slow, soft hug.
Chip Darnell: Oh, it's an escalator. The food rides up to the second floor of the mall, right past the shoe store.
Dr. Nina Byte: Step two. When your tummy is mostly empty, gas and liquid slosh around inside.
Chip Darnell: So the escalator is closed and the pretzel stand is just sitting there, full of air.
Dr. Nina Byte: Step three. The squeezing pushes that gas along, and that makes the rumbly noise. Per Wikipedia, it's gas and fluid moving through the intestines.
Chip Darnell: The mall loudspeaker! Attention shoppers, the pretzels are free in aisle nine!
Dr. Nina Byte: No. Step four. It's louder when you're empty, because there's less food to muffle it. The food is not shoppers.
Chip Darnell: Does the rumble have a name?
Dr. Nina Byte: That's... actually a great question. Yes! Doctors call it borborygmus. Try saying that five times fast.
Chip Darnell: Borborygmus. That's the best food court name I've ever heard.
Chip Darnell: Does Borborygmus Plaza have free parking?