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'Invisible Wall' Acoustic Phenomenon

Years ago I heard a weird tale of an inexplicable phenomenon. A student in a university dormitory was washing his face in a sink, and when he turned on the water, the pipes started oscillating. (The outdoor faucet in our own house does this too, so it must be quite common.) He rose from his bent-over position, then banged his head upon an INVISIBLE CEILING!!! There was some sort of horizontal "barrier" keeping him from rising to full upright position. He turned off the loudly-oscillating water tap, and the barrier vanished.

He was certain that the "barrier" had something to do with the noisy pipes, but he was never again able to reproduce the effect.

I'm repeating this story from memory, so some of the details might be wrong.

A couple of years ago I heard a report of a similar occurrence, but this time involving electrostatics. An engineer was called in to a 3M factory to solve a static-buildup problem in a wide web of moving plastic, and part of the problem involved an 'invisible wall effect' which appeared under the wide strip of plastic which was moving overhead.

In thinking about this late at night, a possible explanation suddenly appeared to me: superpose a string of harmonic standing waves.

In case it's not obvious: the following is untested, crazy speculation, created by major sleep deprivation mixed with conventional physics/eng training. Should it be tested? Sure, if you already had the necessary equipment set up for some other project! At least try to duplicate RW Wood's "visible silver membrane" ultrasound phenomenon from 1939.

On the Possibility of Creating "Virtual Barriers" via Superimposed Acoustic Standing Waves

William J. Beaty, 9/17/1999

A spike-impulse or "delta function" has an interesting frequency spectrum. It is composed of all possible sine waves of frequencies 1,2,3,4,etc. When a large set of sine wave signals are all added together, they cancel out everwhere except at the zero location (origin) of the graph. There they add up to create a large transient-spike.

An acoustic resonator such as an organ pipe contains a type of sinusoidal standing wave. Resonators also support a number of harmonics, and many standing waves of shorter wavelength will "fit" in a single organ pipe.

If we combine the "organ pipe" physics with the "delta function" idea, something very weird results. If the harmonically related acoustic standing waves in the organ pipe are chosen so as to produce a pressure-maximum at the mouth of the pipe, that pressure-maximum will be very small in thickness, like a membrane across the end of the pipe. If the audio amplitude is high in intensity, then the absolute pressure in that thin membrane might become so high that the waveform excursion approaches both two atmospheres and vacuum. It would be a sort of "shock wave", standing wave and it would act to reflect the sound back into the organ pipe as if it was an invisible wall. When viewed at an angle, it would appear silver because of internal reflection during the near-vacuum portion of the pressure excursions. It might even resist penetration by solid objects. Just by transmitting the proper sound into the organ pipe, perhaps we would see the system "self organize" and produce the thin "pressure membrane" across the mouth of the pipe. Or perhaps we need some sort of nonlinear trigger in order to create the "wall".

Shades of Star Trek! "Modulate the shield harmonics henson, their matter annihilation beams are getting through!"


No, this has not been tested. It is pure speculation. Well, maybe "impure" speculation, because there is an empirical component contributed by the anecdotes about strange phenomena.

The harmonics for such an effect would be 1,3,5,7,9, etc. However, if an emitter was in the center of the organ pipe, the "phenomenon: might occur at the location of the emitter, and sound would not get out. To prevent this, we could guarantee that the pressure wave at the emitter would be very low by generating two sets of harmonics, where one is 180deg out of phase with the other. Frequencies would go like this: +1, -3, +5, -7, +9, etc. At the emitter the acoustic impedance would be very low (all wind, little pressure), while at the mouth of the pipe it would be very high, and nonlinear effects might arise (it might become a sort of vibratory acoustic soliton.) A simple way to do this would be to use a double-ended transducer, like a loudspeaker cone, which was stretched across the center of the tube.

I think to myself, "this is crazy, because the standing waves will simply form a travelling pulse." Yes, maybe. Therefor, here's another way to visualize the entire situation. Place an acoustic transducer membrane across the center of a long tube with plugged ends. (Perhaps use a small, disk-shaped electrostatic loudspeaker.) Use it to send out a brief, negative-going pulse which travels down the tube (and a positive pulse will propagate out the "back" of the transducer simultaneously). The pulses will reflect from the plugged ends. As the reflected pulses pass the transducer again, we generate another pulse which propagates in the opposite direction from before (so it moves with the reflected pulses, and superimposes so as to reinforce them.) The pulses are now twice as large. Keep going, and the bouncing pulses will grow and grow until nonlinear phenomena will appear at the tube plugs where the pulses must superimpose upon themselves during reflection. (They also superimpose when they pass each other at the transducer, but then a positive pulse is passing a negative pulse, so the pressure averages to zero, even though the velocity of the gas at that location is high) Then, when the expected nonlinear disruption appears at the tube plugs, remove the plugs, and the nonlinear disruption will form an "invisible wall," a wall which still reflects the pulses.

A photograph of this membrane-shaped nonlinear disruption possibly exists. It is in the book "Supersonics", by R.W.Wood, 1939. In Fig 10 on page 26, an air-jet ultrasonic whistle is creating a standing wave just outside the mouth of the whistle's resonant cavity. It appears as a ring, a flattened donut with a reflective silvery surface which hangs in space.

I haven't thought this through, but it seems as if the sound would mostly cancel out between the emitter and the "invisible wall." The sound within the "wall" itself would be intense, and the "wall" would store a considerable amount of energy inside. Only a small amount of sound would propagate between the "wall" and the transducer to feed any losses and keep the "wall" alight.

Another issue: the speed of sound in a tube is not constant for all frequencies. Rather than pulses, we might need to generate a sort of comb-spectrum which, as it flies away from the transducer, only assembles itself into a narrow pulse as it collides with the tube plugs. This would resemble an "antichirp" wave, but rather than having a swept frequency, it would take the form of a superposed string of repeated "antichirps" which repeatedly slam into the nonlinear region of the "invisible wall" membrane.

This has connections with the realm of EM physics. Nikola Tesla discovered that a long coil of wire behaves as a sort of "electromagnetic organ pipe". If we create the same set of harmonics as above, but make them propagate along a long Tesla coil, we would simply create a corona discharge at the tip of the coil, just as Tesla coils are known to do. However, what if we "modulate the field harmonics" a bit so that the voltage maximum does NOT appear at the end of the coil, but instead appears a few inches away? In that case the "delta function" shockwave effect would produce a membrane-like hemispherical region where the EM fields were extremely intense, but which were nearly zero elsewhere. As the drive frequency was lowered, the hemispherical corona discharge would slowly expand from the coil's terminal, and would inflate itself into the region surrounding the terminal.

But this is impossible! The speed of light is independent of frequency! But is it really? Is the phase velocity within a resonant cavity constant across frequency? No, and narrow EM pulses turn into "chirps." This is nearfield dynamics, and is different than "Hertzian wave" physics. My intuition is telling me that this effect is nonlinear in such a way that "membranes" can be created when a set of superposed waves in constant harmonic and phase relation to each other will repeatedly assemble into a narrow pulse which has a particular physical location. At first glance it appears that a nitrogen gas environment is needed, and the pulses create a membrane made of plasma which reflects the waves. But my intuition says "no, there is an electromagnetic nonlinearity to the vacuum, and only EM fields are needed, no ionized gas is required." Eh, that's impossible. But if actually true... wow! Where is this nonlinearity hidden within Maxwell's equations? I don't know. Maybe within the infamous "tensor version", rather than the simplified version created by Heaviside/Hertz and Co.

If the fields were strong enough, the membrane-like region might glow with purple light... just like Tom Bearden says it does when the Russians use stolen Tesla technology to create a "scalar force bubble." Hey, maybe the infamous "Russian Woodpecker" was a Tesla-bubble generator. Maybe the small modulation of the Woodpecker signal was not data, and not OTH radar, but was actually a method to prevent jamming/disruption by Tesla-technology countermeasures. Maybe the Woodpecker was left slowly ticking over so the nonlinear bubble-effect would remain "alight", but with the power level set so low that any intruding aircraft would pass through unaffected. Step on the gas, and any aircraft would bounce off (or incinerate?) Crazy stuff.

Are you very afraid yet? As Yoda said, "You Will Be."

When applied to audio, it appears that a delta-function resonance membrane need not sit at the end of the organ pipe, but might be coaxed to hang in space. If the frequency of all of the harmonics in the drive waveform was smoothly lowered simultaneously, then the entire "bubble" would expand as if it was being inflated. Hey! Decreasing the harmonics is actually just sliding the comb-spectrum downwards in frequency, and then the lowest harmonic falls off the end at zero freq., and the "bubble" has expanded by one wavelength. Cool. The "bubble" can take any one of a number of concentric locations separated by 0.5 wavelength. (When random intuitive speculation makes this much sense, it's frightening!)

The acoustic membrane-effect might act like an invisible ceiling in any resonant bathroom which was excited by the noise of oscillating water pipes. The higher harmonic energy would have to be strong in order to make the "membrane" be thin. The high frequency part of water-cavitation noise is known to be intense. The pulse waveform of the pipe-sounds would have to resemble narrow spikes, and would have to be resonant with the vertical mode of the room. (Ooo! "Pulse waveform!" All the Tesla-fanatics know that pure sine waves are "Hertzian", and narrow pulses are "Tesla-nian". Repeated pulses might create nonlinearities where sine-wave resonances would not.) And finally, something nonlinear would be needed to trigger the formation of the initial shock-bubble. If the acoustic energy already trapped in the room was intense, maybe the extremely brief "snap" sound of a static discharge could form the "wall".

Going back to EM again, I see that a complete sphere might be possible. It doesn't look possible at first sight because a single dipole emitter would create a pair of "Tesla domes" with a dead-band at the equator of the bubble. However, multiple orthagonally-oriented emitters might be able to create an entire set of "tesla domes" of various orientation. Which means...


...ball lightning is explained! (I didn't know I was going to write that. I'm running in lunatic-mode. It just came out of my fingers.)

In order to trigger production of an electromagnetic soliton-membrane sphere, we'd need to create a huge amount of short-wavelength radiation. The standing waves which would be trapped inside a small sphere of ball-lightning would be of microwave wavelength. This was actually Nikola Tesla's recommendation which was followed by the Corum brothers in producing artificial ball-lightning: they used a pair of frequency-mismatched tesla coils which tended to produce discharges of extremely short pulse widths and extreme power. (when a discharge united the coils, the resonant frequency of the system as a whole was not 2F or 1/2F, and so the EM energy dumped instantly into the arc channel, sort of like Quantum wavefunction collapse.) If a short enough electromagnetic "whip crack" signal could be produced, then a "tesla bubble" might arise, and the electromagnetic standing waves would remain trapped inside. Don't touch the glowing spherical blob, because if it disrupts, the "flashbulb effect" (EMP) might melt your tooth fillings and singe off your eyebrows, as well as dumping energy into the remaining spherical plasma and producing an immense acoustic "bang."

Even scarier thought: what if space is nonlinear for intense EM waves? (It certainly is at the higher energies, where gamma ray EM waves can trigger the production of electron/positron pairs directly from the vacuum.) The above "shockwave bubble" resonant effects rely on the nonlinear behavior of air. In the case of sound, the variation in propagation velocity is the source of nonlinearity and the key to the production of shock wave bubbles. In the case of EM, we must rely upon the formation of a corona discharge which then reflects EM back to the emitter. However, if there is any nonlinearity in the vacuum, then an EM "shockwave bubble" could be produced even in a hard vacuum. Maybe a "ball lightning" can exist even in a vacuum? And if THIS is true, then it implies that atoms are perhaps nothing more than tail-chasing electromagnetic waves which are reflecting from themselves and remaining trapped in one location (and which, when disrupted, can trigger the pair-creation of electrons and positive nucleii?) Are atoms a kind of tiny "ball lightning?" Are they made from little else but light waves? Is "ball lightning" a kind of naturally-occurring giant atomic particle?!!!

There are stories of "ball lightning" passing through windows and walls, and even being "sucked up" by metal wires, only to reappear at another spot on the wire. If this stuff is nothing but an EM wave and a nonlinear effect, then we might expect it to pass through any insulator as if it was not there. It might even launch its waves down a conductor and the re-assemble itself at the location of an impedance-mismatch.

If all of the above is true, then we can make "Star Trek Force Fields" from either EM or sound. Now we just need some phasers to complete the picture. Why not create some charged carbon clusters in a vacuum, accelerate them with some linac electrodes connected to a 10MV tesla coil (in oil), then let the particle beam exit through a tiny pore in the side of the accelerator tube? It would be just like any other particle beam, but because the "particles" could be billions of times heavier than an atomic nucleus, the beam power would be delivered as heat and mechanical disruption, not as "radioactivity" or electric shock. Build a 1000-watt unit and use it like a razor blade. Only THIS razor blade lets us sculpt titanium as easily as we can sculpt butter. Buy yourself a big block of steel and hand-whittle yourself a car engine.

Tesla claimed that he could prove the reality of his "death ray" by producing an incandescent spot on the dark part of the moon which would be visible by telescopes. Heh. This would only be possible if the 'Lunites' weren't protecting their real-estate with electromagnetic Tesla-bubbles!


TO CLARIFY: at high power excitation, a 1/4-wave microwave waveguide produces extreme e-field at the open end and large current at the shorted end. If electric discharge should break out, it partially shorts out the open end, producing an RF-reflecting plasma, and flipping the resonant mode from 1/4-lambda to one half. Does the arc persist? If so, its position will vary with the drive frequency. Lower the frequency and see if we can inflate a "thin plasma bubble" in the space just outside the open end of the waveguide. Maybe it will become an electrodeless discharge: a spark hanging in space, where the spark only exists because it's producing a standing wave, and the standing wave exists because the spark is being a reflector. OK, now try the acoustic version: a thin membrane of standing-wave "AC shock wave" just outside the mouth of a quarter-wave organ pipe being driven by a transducer at ?few hundred watts? A submerged version might be far simpler, since the "membrane" effect would simply be a disk-shape region of cavitation.
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