Why is my lower abdomen making farting and rumbling noises?

It is normal and the medical term is "borborygmi". From Latin/Greek. The guts constrict and then relax to mix up and move contents thru you gut. The chemical digestion produces various gasses depending on what u have eaten and you gut biome. When gases are generated they will make gurgling sounds which are called borborygmi. Now u can use more polite in some circles when you discuss it. :-)

Such noises are a normal phenomenon. If you have too much gas, you can adjust your diet by visiting this site for information. Fodmap: https://www.hopkinsmedicine.org/health/wellness-and-prevention/fodmap-diet-what-you-need-to-know