This actually has a name = borborygmi.
My father was always plagued with it, and mine got worse in my teens. Usually a combination of your own genetics and what foods and drinks you are consuming before hand. My tummy is being very vocal right now, and it is far from hungry. just had a big supper.
it can be louder when you have an intollerance to wheat, barley, lactose etc So playing about with your diet and keeping a diary of effects may show up which if any foods are making things worse for you inside may help calm things down, but the opposite problem of not having any grumbles and rumbles is definitely a sign of problems.
It is normal for everyone to have some degree of noisy guts. Some of us are a lot noisier than others it would seem unfortunately.
If you have other symptoms besides the embarrassment factor then do ask you GP about it, but for the vast majority of people they do get it and do ignore it as there isn't much you can do about once it is in full chorus. It can happen on an empty stomach and full one.
Exams at school and college were the worst times for me. large hall, everyone very quiet then my stomach starts dancing a jig and I try and prod my guts or use my non writing arm to hold my stomach tightly to try and keep the noise from disturbing everyone else and me. i just got used to it, and these days I just ignore it. I might apologise if I am in polite company and my tummy is being over active, but usually I don't bother.