Holographyforum.org / holowiki.org

Dolphins have been doing this in their heads, in real time, for twenty million years. And, not only are they generating a 3-D image of their surroundings in this way, allowing them to accurately navigate in three dimensions without the use of their eyes, they are using multiple frequencies, in effect, seeing in "color". Why do you think their brains are so large? It takes a LOT of processing power to do all that "on the fly", so to speak.

Acoustic holography does actually exist, I worked with such a setup at Peugeot Research Center in Paris some years ago.
While you need a reference beam in optical holography in order to record the phase of the object beam, there is no such need in acoustic holography since an array of microphones are able to record both amplitudes and phases of the incoming sound waves. That makes the setup much simpler.

So you place an array of microphones in front of a scene (say a car with the engine runing), you record the incoming sound waves, apply some mathematics to process the signals and you are able to compute a 3D map of the sound sources locations. Very nice tech

Be careful! People will start yelling at you that this is not a hologram! Just joking, but there are some who see themselves as holy warriors trying to purge the airwaves of anything that's "not a hologram."

Anyway, it's hardly new. It's known as cymatics:
https://www.youtube.com/watch?v=uENITui5_jU
https://www.youtube.com/watch?v=M4F0A1G5i8U

And this is especially interesting:
https://www.youtube.com/watch?v=nxrKeLBbsD4

This sounds like fun (pun intended). http://www.smithsonianmag.com/smart-new ... 63/?no-ist