"What do you mean by "pushes away at the atmosphere to fly and probably doesn't touch the air, thus no shockwave" ? I mean ANY material object moving through a medium would cause its displacement.
Unlike most students, I'm probably one of a few that actively thinks about UFO technology throughout my educational career applying known Physics laws & observations wherever possible. While I explain this, there is a chance that I may go off topic, but since I brought it up then technically I have not broken any rules...
Look around, our planet's gravity holds in our atmosphere, without it we would not be here. That is not to say that other celestial bodies with gravity automatically have an atmosphere, look at our moon. All planets in and outside our solar system (those that have been detected) have atmospheres; but hostile, which means we cannot live in them.
It seems to be a widely held belief that those vehicles identified as UFO's (which seems like an oxymoron to me), run on a propulsion system that we are not capable of duplicating. I have my theories, but it seems that these vehicles generate an effect of lack of gravity*. That is, outward instead of inward, unlike the current understanding of gravity. Anyways, since it is gravity that pulls air to earth, then an 'anti-gravitational’ vehicle will push air away from it in all directions, thus no air will touch it. **
But then how does it move? Well consider that an aircraft has more that one force to keep it in the air, one is the engine, and two is the wing. There has to be at least one more 'gravity generator' to force it along. That would be the DISPLACEMENT you were asking about, it might be reacting to something that has to be common on all celestial bodies in space: A magnetic field. However, our mag field is very weak, if anything, that craft would have to amplify it via some ferromagnetic material with a high magnification constant.
Hope it helps you understand what I meant. The scientific term for this type of engine system is called "Field propulsion", though you won't find much of UFO-tech, look it up.
*I don't like to say 'anti-gravity' that cuz our science says gravity cannot be generated, it is dictated by mass. Their machines must be reacting to something that gives us the impression of being against gravity -- I'll bet it has nothing to do with gravity.)
**Once you're a certain short distance away from the craft the atmosphere will be restored. Like the air behind a plane will be restored after the vortex swirls calm down. Sound needs air to travel so you wouldn't hear it if it were above you. But then theoretically you wouldn't be able to breathe either, as there is no air in the local region around the craft. A vehicle like this would experience no friction from the atmosphere whatsoever.
The meaning of life is curiosity; we were put on this planet to explore opportunities.