WIederling wrote:GE9X is running in idle ( cue the unchanging whirligig pattern on the test specimen.)
while the original engines spool up.
That's not what GE says, and they're right: look more carefully at the fan blades of the GE9X. You can see them speeding up through the strobe effect caused by the camera's frame rate.
From GE's caption to that picture: "This is the #GE9X going to takeoff power on the run pad last week in preparation for its second flight test campaign."
That is also certainly not what three CF6s sound like.