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engineer fag here
I have used this technology from Holosonic for many years. It's referred to as directional audio - and it uses ultrasonic sound waves that are tuned to become audible at a set distance. It IS NOT "in your head" - as it is very much so audible in a small target area. It is used in museums etc. where audio would be too annoying or disturbing to all as traditional audio. You can reflect the sound - Eg. you could make it sound like a dog is barking in someone's house by bouncing the sound off their front door or other structure at the right distance. At the point of the "reflection" it can be tuned to be audible at just the right distance. But you could literally move your head 2 feet and hear nothing, and move it back and hear clearly. It would be very easy to figure out and near impossible to have 'travel' as you move about. I believe this is purely something done while in therapy at Henderson mental health facility.