The engine has more than three settings folks (AB, MIL and IDLE)..
A lot of aircraft will howl at just the right throttle setting and in certain conditions, like the F-15. F-15's will howl on approach similar to the Hornet. See below...this is fairly minor for an Eagle howl, I've heard it much, much louder.
You can also hear it at 2:06 in that video.