Acoustic levitation dates back to 1866, with "3d shape" demos, like this, going back at least 20 years. This concept is used extensively in quantum computers, and for suspending and manipulate small things, but with lasers and radio waves rather than sound.
You should try a VR headset, for a glimpse of the future of 3d displays. ;)
You should try a VR headset, for a glimpse of the future of 3d displays. ;)