Introduction to sensory reciprocity in intelligent sensing

Make your own veillographic or meta-veillographic sensory system

Some of the students have been asking quesitons like "how does the sonar transducer know whether to receive or transmit?".

There seems to be an apparent myth that transducers must always contain some kind of intelligence, as illusrated below:

in that there's a popularly held myth that all transducers must contain artificial intelligence AI that selects from among an actuator, A, or a sensor, S, depending on whether it a signal is fed to it or from it.

In actual fact, many transducers obey a principle of reciprocity.

It seems to come as a surprise to many that a transmitting antenna can receive, or that a loudspeaker can work as a microphone, or vice-versa.

But take a look at modern radar imaging systems and you see that they transmit and receive out of the same antenna at the same time.

Most typical antenna systems can receive as well as they transmit:

''A cryptic sentence (''We have seen Mary Baker Eddy with one eye'') was inserted into a commercial short-wave broadcast to inform British Royal Radar Establishment of the invention of the T/R (Transmit/Receive) switch allowing a single radar antenna to be used for both transmitting and receiving (having seen the Christian Science building with just one antenna).''
==Five years at the Radiation Laboratory (1946, M.I.T.)

Likewise, modern sonar imaging systems transmit and receive through the same transducer, as your fellow student Derek demonstrated in the lab.

Yet many people are surprised to discover that the same loudspeaker installed in their condominium, hotel, or apartment can very easily be used as a microphone to listen to their conversations.

Take a look at the original telephone

It consists of a vibrating diaphragm and an electrified magnet with a spiral wire that wraps around it. The vibrating diaphragm alters the current of the magnet. These alterations of current, transmitted to the other end of the wire, create analogous vibrations of the receiving diaphragm and reproduce the word.
==Antonio Meucci, 1857

In other words, the speaker and microphone are identical, and conversation can be carried both ways.

You should try the following: Connect two speakers, one to each end of a long wire in acoustically isolated spaces. When someone speaks into one of them loudly, you can faintly but definitely hear the sound in the other speaker, and vice-versa.

For this lab you will use your existing vision system for the blind, in such a way that you can see and photograph the invisible ultrasonic sound waves from your system. Being able to see and photograph sound waves or radio waves, e.g. radar, is called veillography, and the scientific study of data collected in this manner is called veillogrammetry.

To do this, you will build a wave display machine, known as a S.W.I.M. (Sequential Wave Imprinting Machine) from a number of LEDs (Light Emitting Diodes) arranged in a linear array, thus making a voltmeter:

Only one light should be on at any given time, or at most two (e.g. while it is transitioning between voltages). Input voltage should be limited to 0 to 5 volts so as to prevent damage to the voltmeter and to prevent erratic display behaviour.

The unique thing about this kind of voltmeter is that it produces its own light source, so that when you wave it back-and-forth, it is visible as a trail of light, so that you can see and associate it with the measured quantity.

Take your setup from Lab2, and take the receive transducer of Lab2 and extend it with a long FLEXIBLE MULTI-STRAND pair of wires, ideally twisted-pair. (If you did Lab2 with just one transducer for both transmit and receive functions, extend that one transducer with a long FLEXIBLE MULTI-STRAND pair of wires, ideally twisted-pair.) Mount the transducer to your self-illuminiating voltmeter, as shown below:

Now when you wave this self-illuminating voltmeter back-and-forth while it is attached to the transducer that is moving with it, you will be able to actually see the sound waves coming from the other transducer (or coming from reflections off objects if you are using only one transducer as both the transmitter and receiver).

Links:

https://www.instructables.com/id/Seeing-Sound-Waves-Bug-Sweeping-Robots-for-Augment/
See Section 4 of this Instructable, on how to make a SWIM: https://www.instructables.com/id/Imprint-Invisible-Sound-and-Radio-Waves-Onto-Your-/

Grading

Assembly of the self-illuminating voltmeter prototype on breadboard, neatly wired, and well-done, 4/10

Visual demonstrataion that you can see sound waves, while waving the unit back-and-forth, 4/10 (here [link] is what it should look like).

Photograph of the sound waves, 2/10

Bonus marks (for a grade higher than 10/10): Possible ideas:

Complex-valued self-illuminating voltmeter, e.g. use Red LEDs for Real, and another colour for imaginary, so we can see complex-valued electrical signals;
Extended range, e.g. 20 or 30 LEDs;
Meta-veillogrammetry and meta-veillography: exchange roles of transmitter and receiver. Mount the transmitter to the self-illuminating voltmeter and wave it back-and-forth while keeping the receiver stationary. Explain what this means and what it is that you are measuring;
Demonstration of metaveillographic or metaveillogrammetric analysis using machine learning.