Acoustic Rocket Demonstration -- revisiting Dvorak's 1878 Acoustic Repulsion Apparatus

This demonstration was presented on Dec. 9, 2020 as part of the Acoustical Society of America "Acoustics Virtually Everywhere" online conference.
Abstract:
When a Helmholtz resonator is driven with sufficiently high amplitude, the pressure difference between the inside and outside of the resonator and the non-uniform oscillating flow of air into and out of the resonator opening results in a reaction force on the resonator akin to rocket thrust. The earliest demonstration of “acoustic repulsion” using small Helmholtz resonators was reported by M. Dvorak in 1878 [Phil. Mag. Ser. 5, Vol. 6, No. 36, p. 225 (1878)]. Lord Rayleigh explained that the average pressure inside the resonator is higher than the external atmospheric pressure, with the result that the “resonator tends to move as if impelled by a force” [Phil. Mag. Ser. 5, Vol. 6, No. 37, p. 270 (1878)]. This demonstration will show an updated version of Dvorak’s 1878 apparatus using Christmas ornament balls as suggested by Uno Ingard, [Notes on Acoustics, (Infinity Science Press, 2008), pg. 336]. In addition to showing the resonator rocket in action and discussing its history and various theoretical explanations, this demonstration will show how the amount of “thrust” may be measured with a mass balance and will attempt to visualize the flow in the neck of the oscillator.

[@ihmejakki2731]

Thank you for this wonderful demonstration! I'm very eager to try out the setup displayed at 8:45 when the labs open up again!

[@richardalbertoriveracampos3517]

If you put an empty bottle close to your ear, you will note how it resonates with ambient noise and amplifies its natural acoustic frequency, I wonder how much power it is necesary to produce this propulsive reaction with white or pink noise. Nice job, congrats, keep on!!

[@zippolag]

this is just amazing, I can't believe it's not a more widely-known phenomenon!!

[@убиватьрускуюсвиню.Русняетопол]

doesnt the tin can phone work like this?

[@h7opolo]

suppressed energy technology for profits of oil industry. not for much longer...

[@TheHerosDeath]

Super cool! Thank you for sharing! Do you think you could set up a table top experiment for kids with a blue tooth speaker and a tone generator app? Maybe using smaller ornaments and a thimble.

[@DanRussellPSU]

I highly doubt that a blue tooth speaker and a tone generator app can produce a loud enough signal to make this work. Smaller sized ornaments would require a higher frequency -- but the two most important parts are: very lightweight resonators (the bulb ornaments I used in this demo were about 10-12 grams) and a very loud sound source at exactly the right frequency. That's why I was using a big loudspeaker driven by a very powerful amplifier. In order to get these balls to rotate, I had to produce a (dangerously loud) sound in excess of 115 dB (30 times louder than the level at which hearing damage occurs). At the end of the video you can see that I was wearing heavy ear-muffs to protect my hearing while the sound was turned on. My big loudspeaker was starting to smell (burning wires) because I had so much current running through it to make the balls and bottles rotate.

[@TheHerosDeath]

@@DanRussellPSUYeah, that’s not too kid friendly... Thermal acoustic solar organ might be a little bit safer and interactive while covering similar ideas. Thanks again for the reply and amazing videos!

[@Greg_Chase]

Here's the conversation: RESONATOR: "Okay here comes the air. Pulses of air molecules pushed by the speaker." SCIENTIST: "So - air enters. What's your next move?" RESONATOR: "The air comes in. It's gotta go right back out, I"m only open at one end. The other side is closed off." SCIENTIST: "Air comes in, air goes out. Anything else?" RESONATOR: "Try that in a vacuum."

[@SOME_WORDS]

Cool, thanks

[@Resonanttheme]

What explorations into an ideal shape of the resonator would be conducive to producing the the most thrust I wonder?

[@BenInSeattle]

Very nifty! Does this work with complex, non-repeating soundwaves such as music? I think it could be beautiful to have a physical visualization of the audio spectrum by using an array of tuned Helmholtz resonators moving up and down, sort of like a Galilean thermometer for sound. Would that be possible? It looked like the decibel level required to induce the jet flow was much higher than everyday sounds. Could one lower the volume needed by using a different cavity or neck shape, or perhaps a different material? Or should I just stick to tuning forks and deflecting mirrors?

[@h7opolo]

3:14 what's his first name? i found out the "V" stands for "Vinko".

[@DanRussellPSU]

Great. All I have e been able to find on any of his publications was “V”.

[@TheTrumanZoo]

i wonder if we mounted 2 or 4 normal standing speakers directly onto a spinning platter.... we would probably get a spin going?

[@АнатолийНауменко-л9о]

Дети собирают квадрики и летают на Марс, а взрослые дяди открывают для себя акустический резонанс. ))

[@DanRussellPSU]

rough translation (Google Translate): "Children assemble quads and fly to Mars, and adults discover acoustic resonance"

[@omegafile]

Would you like to see my 1 terrawatt acoustic engine that makes it's own water and turns it into hydrogen and burns it for feedback of sound? It has 13 non moving parts that can be reproduced.. I have the CNC codes. You would just have to ask the machine shop to make the parts... you don't need to plug it in to start it you just have to sing to it until it gets hot and then it will never stop..... you could wack the xylophone key but then you would be too close to it and it would hit you with a bolt of lightning.... It's surprisingly small.. 2 ft high x 1 ft diameter... and no coils or wires.. I use other types of ways to generate the high voltage and the vibrating electromagnet that is water cooled. It makes hot water air, gravity and electricity... possibly slows time... I think I cracked that one too... It was too easy to engineer... seriously simple. I think i was 7 to 12 years old when I figured it out....I tried to get others to help but nobody wanted to help at all.. and so I had to do it all myself... and here I sit for at least 3 decades with the solution to the green energy problem and everyone is too cheap to put a penny into it and too lazy to spend the time. There is no free energy.. you can't get something from nothing.... it burns water... and from the simple magic of science it also makes it... and uses the same water over and over again and never runs out. You just have to look at a doughnut with the hole in the center.. the sound is going upwards and the feedback is coming back up the hole at the bottom... too easy. It's the snake eating it's own tail.. the snake representing vibration and the eating of the tail representing feedback. The power of your voice alone.. can move mountains. There are some simple tricks to use..wood vibrates when it gets hot.. and gold becomes magnetic when it gets hot while iron is not... so then a tuned box with an air hole on top lined with gold becomes a vibrating magnetic field when it gets hot.. and once the box gets hot inside all the cold air goes to the bottom hole and all the warm air goes up the center and blows a horn onto the underside of a heavy xylophone key that bounces on some disks.... and more.

[@mememan2344]

Would you mind sharing those files?

[@omegafile]

@@mememan2344 you tube is blocking my reply...how do I contact you?

[@omegafile]

@@mememan2344 I don't have the balls to make a you tube video about it. I don't think they will allow this out. look at the galaxy.. it has a black hole.... it's thermoacoustic.. we are being lied to. This device is a doughnut inside a box.. it has a black hole and everything gets sucked into it.

[@mememan2344]

@@omegafile it keeps deleting mine as well...hmmmm

[@omegafile]

@@mememan2344 im on linkdin as Gamer Kingdom