Feature-Based Passive Animation Go to Dolphin Inspired Sonar or Quick Overview.

Dolphin-Inspired FBP
Feature-Based, Passive Sonar

Sonic Imaging Animation of 07 May 2013
This is not make-believe. If the data-files of simulated echoes were replaced with data-files from real echoes of clicks of dolphins, images would be computed.

See the sort of echoes that were used.
The duration of the Fang in each click is 1/100,000 second as in dolphins - which suggests a frequency of 100,000 cycles per second, if the click were a sine wave.

The array of sensors used here is smaller (19 rather than 36 sensors) than those of the simulations of April 2013.

This is, so far as I know, the nearest simulation in the world to what dolphins are actually doing with their sonar (Correct me, if I am wrong: doug@DolphinInspiredSonar.com ).
And this is just the beginning.

The grid-spacing in the picture is 6 inches.
The diameter of the array is merely six inches. The distance from a sensor to its nearest neighbor is 2 inches. Thus, the size seems, since April, to be shrinking to match the face of a dolphin?

The target is a white, skeletal fish. The colored dots are what the FBP software computes from the simulated echoes.
A side view of the actual, simulated, skeletal, fish is in the lower third of the view.

A bag of tricks, not yet used here, exists for improving the picture from the given data. The occassional glitchy phantom dots can be removed by later versions of the program.

Please remember that some limiting characteristics of the images have to do with keeping low the time the experimenter waits between his tests.