Feature-Based Passive Animation
Sonar Inspired by Dolphins
Simulations by Douglas Moreman
Click a picture to enlarge it:

1) Active. sonar 2005

3) Dual. April 2013 B.

2) Dual. April 2013 A.

4) Passive. May 2013

These are not animations of art. Each frame is computed from "real" simulated echoes.
The same software ought to give us a picture of an object that a real dolphin is clicking on, if echoes from that object were fed in as input.

Can you find a "fang" in this
simulated click of a dolphin?

The duration of the "fang" part of the 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.

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:
dmoreman@aol.com ).

The grid-spacing in the animations is 6 inches.

The target is a white or gray, skeletal fish. The colored dots are what the FBP software computes from the simulated echoes from that fish.
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.

Some limiting characteristics of the images have to do with keeping low the time the experimenter waits between his tests.