For example, should I try to find a diet that does not cause these noises? Maybe the sounds are indication of non-optimal food combinations that has an impact on dietary value?
Stomach rumbles, or to give them their proper name of boborygmus, are the movement of gas and fluid in the intestines. This is a normal thing. Most of the time they are not loud enough to be audible, but they can occasionally be heard without the aid of a stethoscope.
It can also occur with incomplete digestion causing excess gas, excess swallowing of air, or when your stomach is empty and you are hungry.
There are a few diseases that can cause rumbles, such as persistent diarrhea, celiac disease, Crohn's disease. I would not worry overmuch over the occasional noise, but if there seems to be a lot of it, and possibly accompanied by other symptoms such as excess flatulence, diarrhea, pain, I would have it checked out by a medical professional.