low whistle when driving down road on 1998 Chevrolet Astro

there is a low whistle noise when driving down road sounds like power steering but it has plenty of fluid when the gas tank is at least half full the sound seems to be a little quiter could you tell me what it is

Asked by for the 1998 Chevrolet Astro
could be the fuel pump on its last legs. i would get it checked asap before it fails completely.