Andrew from Ann Arbor, MI asked about a noise whose frequency was not directly related to vehicle speed, but rather the load on the steering mechanism. T&R suggested different methods for testing for the noise while the vehicle was in motion or on a dynamometer. Since the former is difficult/unsafe and the latter is not available to most car owners, I was thinking about something simpler.
How about the following:
1) Find a solid section of curb at least 4-5 inches high.
2a) With steel wheels, remove the wheel covers (if any) to prevent damage and park the car parallel to the curb with the wheels against the curb.
2b) With alloy weels park the car with the front wheel close to the curb so that a 2x6 can be used to fill the gap.
3) Without moving the car, gently rotate the steering wheel one way or the other to see if the noise can be reproduced.
4) If so, get an assistant and check further to see if it can be isolated to the power steering pump or the rack.
Good luck.