The Reid wrote:

Following up to Mika

The growling does not come from the stomach, it comes from the
intestine. The intestine contracts to move materials. If there is a
certain proportion of liquid or gas (as is the case if you have not
eaten) the contractions generate the sound that is noticed as 'stomach
growling'.

now I can impress my dentist!

Did a quick check after posting. Since the stomach also contracts, it
may indeed also be the source of such sounds. But in most cases it is
the intestine.

M