Learn English – Onomatopoeia for stomach growling

Cough is onomatopoeic. OED 1, s.v. Cough, v., recites Dutch and German cognates and remarks that “All these words appear to be of echoic origin, representing various sounds and actions made with the breath.”

I suggest rattle:

: to make a rapid succession of short sharp noises <the windows rattled in the wind>
_{Merriam-Webster}