[afishkind]

Questions I've been asked:

AC on, FAN on --> yes noise is present
AC off, FAN on --> Noise is present (press the "AC OFF" button but leave the fan on low)
AC off, FAN off --> Noise is present (press the "AC OFF" button, leave it for a while to stabilize temps, then turn the fan off all the way)

Next diagnosing steps after AC, does it happen while sitting stationary? No

Or only when moving? Yes
Does the noise increase frequency with engine RPM? No
Only happen at certain RPM's? No
During idle? No