For my part, I prefer the IAH way to that of CLT, ATL, and other airports where those same carts are always barreling through the concourses with that infernal beeping, which occurs whether anyone needs to move aside or not. At IAH, at least, the call-outs are only as-needed, and some of the drivers are imaginative enough to ask us to move aside in relatively creative-sounding ways. (Anything's better than the beeping. Gets in your head and stays there.)