2003 Audi A6 noise under driver feet

I'm gonna go out on a limb here and suggest that's not normal. Have the steering and suspension systems inspected at a tire and alignment shop. In particular, for what you described, they will look closely at control arm bushings and struts. While those aren't exactly a safety issue, at least in terms of parts that can separate and lead to loss of control and crashes, worn parts can reduce steering response, stability, and accelerate tire wear. Once we know what is wrong, we can discuss how serious it is and the typical remedies.