If you think sonic booms from supersonic aircraft are a nuisance, wait until the sky is full of planes propelled by up-scaled versions of this interesting but deafening audio resonance engine.
Granted, there’s a lot of work to do before this “Sonic Ramjet” can fly even something as small as an RC plane. Creator [invalid_credentials] came up with the idea for a sound-powered engine after listening to the subwoofers on a car’s audio system shaking the paint off the body. The current design uses a pair of speaker drivers firing into 3D printed chambers, which are designed based on Fibonacci ratios to optimize resonance. When the speakers are driven with a low-frequency sine wave, the chambers focus the acoustic energy into powerful jets, producing enough thrust to propel a small wheeled test rig across a table.
It’s fair to ask the obvious question: is the engine producing thrust, or is the test model moving thanks to the vibrations caused by the sound? [invalid_credentials] appears to have thought of that, with a video showing a test driver generating a powerful jet of air. Downloads to STL files for both the large and small versions of the resonating chamber are provided, if you want to give it a try yourself. Just be careful not to annoy the neighbors too much.
Thanks to [cabbage] for the tip via [r/3Dprinting].
a few questions:
– Assuming this is really “sonic locomotion”, How does the system draw in new air to be compressed and ejected from the chamber?
– How do you know this is not actually linear motion derived from the inertia of the speaker assembly? For example, a sawtooth wave would be an ideal wave shape to tension the speaker assembly, then relax it in an higher energy motion in the direction of travel. Mechanical motion is easily demonstrated with brush-bots for example, but they are merely a fun curiosity, as they are very inefficient.
– Have you measured, and have any data, pertaining to the thrust generated and expelled from the chamber? What is the method of measurement? Simply mounting the whole system onto a load cell would not isolate forward momentum from vibration from thrust generated by air exiting the chamber.
This is interesting fun. But im sure plenty of people have mounted air horns to wheels and called them engines before.. and never got very far. While it is true that jet engines produce a lot of noise, a jet engine is optimized to produce a high thrust to weight. Noise is a byproduct, not what an jet engine is optimized to do. Speakers are optimized to produce high noise to weight. Jet engines are designed such that all of their inertia is directed in one direction. Speaker inertia is divided in two opposing directions. Your “forward thrust” inertia is constantly being partially or fully canceled out by reverse inertia.
Finally, it just seems like a great amount of electrical energy to obtain a small amount of mechanical work, when there are other far more optimal mechanisms. A solenoid, for example, based on the exact same electrical principals, performs more mechanical work in a direct manner. Using a speaker to convert electrical energy into sound, and then trying to subsequently convert sound into linear motion is a very inefficient process.
These things often abuse the fact that ejecting air out gives it momentum and makes it blow straight in one direction, while it gets sucked in from all directions around the nozzle. There is even iphone app, that can blow a candle using just stock speaker and this very principle.
This is essentially a helmholtz resonator which can produce thrust at the right frequency. The action lab on YouTube has a good explanation. I believe the air comes in as a vortex but out in a jet to create thrust. I don’t know how much the Fibonacci curves would help, but mounting a speaker in the bottom of a jug should do the same. You can find the resonant frequency just by blowing across the neck and measuring the sound.
You gotta play Van Halen from the speakers to get sufficient forward thrust.
Or bat out of hell if you want it to go really fast.
This made me LOL.
That sawtooth concept you mention is exactly how vibratory bowls function for sorting parts. It utilizes the difference between static and dynamic friction and is several decades old. Since this project uses wheels, though, it might not be how this one works.
Oh my… That website wouldn’t look out of place in the 1990s. Maybe except the youtube embeds…
You mean that it’s actually useful and doesn’t need 500MB of WordPress resources to load? Yeah, back when function mattered more than form.
I love it.
As far as I can see, this system only has one outlet/inlet. I think on the speaker’s downstroke initially less air gets in than out on the upstroke, until enough air left the engine to create enough low pressure to balance in and out, at which point forward motion would cease. This may be why the clips of ‘invalid_credentials’ are rather short.
This sort of reminds me of the “pop pop boats”, except with air instead of water. Steve Mould did a couple of videos on them, including one with a scaled-up model that he could ride.
yeah pop pop boats are really interesting, and at least without any deep analysis, somewhat counter intuitive. Its this example specifically that makes me not want to dismiss this concept outright. That, and we of course know that speakers can move SOME air.. plow out candles, etc. Air cannons are a thing.. Its just.. everything here feels a little suspect, without much more evidence than the website provides.
You could skip all the silly electronics and dump the power into a heater, to make a thermoacoustic engine. It won’t be any quieter, but I’ll bet it will be more efficient.
Same air-blowing effect from the sub-woofer under my desk : I checked the enclosure, there is no compressed air bottle inside the box, no air intake / ventilator, nothing except a closed box.
So I guess that air coming out must have coming in by the same opening at some point.
Then I checked the bookshelves speakers on the desk : if I set the music very loud, they move forward !
This strange effect is actually caused by the desk not level but a little forward-bent. The vibrations allow an air cushion to form under the speakers with a flat base. This air cushion then makes it easier for the speakers to slide on a sloping surface.
Maybe I could use this effect to travel around the world, but I need a bigger desk.
(congrats for the nice looking website with table-tag design, marquee and animated gif !)
It is the same volume of air in front of the speaker being vibrated by the speaker. This is sufficient for transmitting sound.. much less so for generating momentum, (unless your subwoofer is constantly pushing itself across the floor?)
you’d need a bigger desk, perpetually slanted downward.. and wheels. very low friction bearings. But then yeah! sure.. those speakers will push you along.. assuming no wind. ;)
By calling it an “engine” I assumed there would be some combustion taking place. As mentioned by others, this is just an inefficient, electric, diaphragm pump.
The word “engine” is far older than internal or external combustion engines. It means, in essence, the same thing as “machine”, including something as simple as a lever.
Ramjet
“You keep saying that word. I do not think it means what you think it means.”
HAD comments need react buttons.
So it’s a aircraft version of a put put boat?
Cool!
yea, but it relies on annoyed people yeeting it
On the previous day high tech mouse detection by radar etc. was mentioned. With a short range camera and target, could this mess with the delicate wings of blood suckers at close range? Maybe even flies wouldn’t be able to fly anymore? I call for experimentation. Fans can suck them into a filter but there is no way to have a CO2 emitter at the portal of death because it’s getting sucked away instead of saying come here to feast on warm blooded things. Here a heat source and CO2 will attract them to the target and “poof” another one’s down.
I wonder what sort of decibel levels would this need to be operated on to achieve various results.