Heavy humming in power steering

I recently changed out my reservoir filter and fluid to see if a heavy hum would stop, but by the next day it returned. Could this be a bad pump or pulley?

When I am siting idle and rotate the steering wheel slightly to the left or right I can get the hum to stop, but when I release the wheel the hum returns, has anyone had this issue, and found the culprit?



Thanks,

Pete:

facepalm: