Solving the
Mystery of the Sonar of Dolphins?

by Douglas Moreman


quasi-passive sonar

Videos of Simulations

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To know a solution exists can be a giant step towards finding a solution. -- Anonymous Mathematician

I knew in 2001 that a "clicking" dolphins can "see" an object in the dark by means of echoes of those clicks. Later, I surmised from simulations, and found reports to verify, that a dolphin can "see" in t he dark via clicks of another dolphin. Someone, back then, in biomimetics of the Office of Naval Research, was saying that no one knew a mechanism to explain how such "vision" could be possible.
So, when I was struck, unexpectedly, by a first insight into how information about shapes of objects might be extracted from echoes, I assumed that I might be onto something important and went after it. My first idea was of parallel computing done in a network of neurons (not the popular "neural network"). Not able to simulate such a thing in practical time, I created serial computing methods to accomplish the same ends. In a few months, I was able to simulate a mechanism that produced images, of sorts. That was more than 15 years ago.

Using the US Patent Office, I published an hypothetical biological mechanism and also some possibly practical ways to compute images from echoes of clicks like those of dolphins:
U. S. Patent "Echo scope", was granted in 2008.
Its approach rests on an hypothesis that the brain of a dolphin has a network of special neurons that I call "torons." By operating "in parallel," the torons perform image-making calculations at a speed that is hard to beat in our serial computaters.
More recently, I discovered statistical power in neurons working in groups. This allows the sensing array of an imager of simulated "fish" to be as small as the chin of a dolphin. Now in 2018, I am attempting to publish, in patents, upgrades that increase the opportunities for practical applications.

The methods of solution proposed here begin with this idea:
rather than their ears, torons compare times-of-arrival ("toas") of echoes that arrive at echotrigger sensors in their jaw (perhaps just in the chin).

Experiments with my simulators suggest:
one can replace simulated echoes with real echoes and see, not a simulated target, but an object that a real dolphin in actually clicking on. Perhaps some day, we will see such imaging on display in dolphin aquaria?

A new invention, spun-off from more general developments, is that of a simply-built improvement on existing fish-finders:
Streaming Fish-Finder in 3D. Roughly speaking, simulations suggest that one of these devices ought to be able to replace a "downward" sonar and also have some of the 3D fish-imaging ability of "sidescan" sonar.

Mathematics of the Sonar of Dolphins

This new computational method for sonar and radar, Feature-Based Passive, FBP, enables computation of an image, of sorts, from a single "click," like that of a dolphin. The waves used for imaging are not limited to sound. Ideas for applications include
* the world's best fish-finder and an analogous radar application that can help locate sources of enemy fire.
* high speed, inexpensive imaging for medical triage.

A parallel-processing approach is suggested by the Echotrigger/Toron Theory of the imaging sonar of dolphins.

Since the mathematics applies to waves other than those of sound, a new name, wavar, has been adopted to refer to the wave-related principles and methods shared by sonar and radar.

Wavar, here, is being developed using "experiment-machines" -- simulations software for rapidly crafting and running experiments in extracting visual from information from waves.

The approach is "geometric" in that its calculations use Geometry and not methods of the sophistication of, say, Fourier Analysis.

The new (I think) and simple signal-processing methods herein are "feature-based" and "passive" in that they use times-of-arrival of known features of particular waves and can use, but do not require, knowledge of time and place of emission of those waves. One dolphin can "see" by means of clicks made by another dolphin.

It seems that in most species of toothed whale, for which sonar-clicks have been recorded and graphed, the clicks all have one prominent instance of a feature that I call a fang.

A fang is a change in loudness that goes from a low to a high and back to a low in, typically, about 1/100,000 second and is much greater than all the other low-to-high transitions in the click. There is a fang to be seen in the graph here that represents the sound-pressure with-respect-to-time of a "click." Given the shape of some feature, the "fang" perhaps, but not knowing the time or the place of the emission of a click, FBP can, nonetheless, make a picture from echoes arriving at an array of sensors.

One might wonder if the scope of potential applications of geometric sonar includes sonar, radar, exploration-seismology, and medical imaging?

Email doug@dolphininspiredsonar.com
Douglas Moreman

Sonar of Dolphins

Why "Echolocation" Cannot Explain the Sonic Vision of Dolphins.
Applications of This New Technology.
The Echotrigger/Toron Theory, How Neurons Can Image with Sound.
Abstract: Hypothetical Neurons.
Sample Program for Experimenting.
FBP with Dual Clickers.
Glossary
Baleen Whales MUST have sonar?
Odds and Ends.
"Sonic Imaging," presented at a meeting at Tulane University in 2005. The accompanying animation (2005, below) represents the possible functioning of a "fish-finder" -- it only operated in active mode.
Latest Abstract 2018

3D Animations (also given at the top of this page):
Each of these animations was generated frame-by-frame from outputs of a simulator.
Animation of active sonar at Tulane in 2005.
A first animation of FBP, April, 2013. Uses passive in the top view, active in the side view.
Cleaned-up FBP images, simply obtained (2013).
Animation of purely passive Feature-Based sonar, May, 2013.
No animation is yet, in 2018, available for the newer methods that allow reduction of the diameter of the array to that of the chin of a dolphin.


Thanks in Memoriam, two tutors in the use of sounds for detecting and imaging:
John Gitt, sonar. Westinghouse Oceanic Division
Donald Haefner, seismology. Shell Oil

This web site was begun in April, 2013.
This page of the site was modified on