In the book Daemon by Daniel Suarez a technique gets described, that enables a device to create an acoustical illusion of a moving person inside a house.
Just then a voice called out clearly from the end of the hallway upstairs. ‘Who’s there?’ […] No reply. But they heard walking again. The footsteps came down the marble stairs to their right, some distance away from them. They could clearly see the staircase, but no one was there. They could hear the sound of a hand sliding down the metal railing. […] The footsteps were moving across the floor to them now. […] Then, in midair not five feet in front of them, a man’s voice shouted, ‘You don’t belong here!’ (page 94)
As I searched the internet for more information on the mind-shaking technology described by Suarez, I just encountered papers (and videos) on the use of a single hypersonic sound beam, that creates audible sound where it hits a surface. This leads to an effect that most people describe as a 'god voice' similar to the experience of the use of bone conducting speakers.
However what I am searching for is an answer to the question, if it is possible to create sound in mid air (at a chosen position in 3D space) as the author is shaping the picture of the technology, cited below.
A HyperSonic Sound system – or HSS – does not use physical speakers. HSS pulsates quartz crystals at a frequency thousands of times faster than the vibrations in a normal speaker – creating ultrasonic waves at frequencies far beyond human hearing. Unlike lower-frequency sound, these waves travel in a tight path – a beam. Two beams can be focused to intersect each other, and where they interact they produce a third sonic wave whose frequency is exactly the difference between the two original sounds. In HSS that difference will fall within the range of human hearing – and will appear to come from thin air. This is known as a Tartini Tone – in honor of Giuseppe Tartini, the eighteenth-century Italian composer who first discovered this principle.
PS: The reason why I even bother to search for information about a technology mentioned in a novel, is the author's concern, to just describe technology, that is in development in some lab and not placed in science fiction. He has a website for the description of some technology used in his book.