Ultrasonic Standing Wave Visualisation

This is a video of a third year mechanical engineering undergraduate project at the University of Bristol.

Here CO2 is used to visualise the standing wave created between the source and reflector.

[chrismurray]

@PDopey. Thank you very much for you kind comments, although my thanks is a little delayed. It is correct that I there are 7 nodes, but what I did was use my frequency just into the ultrasonic range and then tuned the height of the gap to get the best possible standing wave. The balls at the nodes are actually made of polystyrene as density was very low.

[chrismurray]

@PDopey. The limit of the amount of balls is just over three. The limit on size is that the object has to be less than half a wavelength, so in theory if you could get a long enough wavelength you could levitate very big objects as the limiting factor of how much acoustic pressure is needed in order to create a large enough force on an object in the wave, is the density of the material just as long as the object is much smaller than the wavelength.

[kubarebo]

The electrons are neither waves nor particles nor anything else that you commonly experience. Their behavior is described by quantum mechanics, and that is unlike anything you'd experience directly in everyday life. IMHO the best explanation is in Feynman's Lectures on Physics. There is audio available for the quantum mechanics lectures. The "explanation" as to how the electrons are "locked" is that if it weren't so, the uncertainity principle could be worked around using electrons :)

[chrismurray]

There is force generated as that is what is pushing the polystyrene balls into the nodes, the balls are sitting at a node of pressure. I have done the experiment horizontally, it is much more difficult as the effect of gravity acts now in a different direction but the force generated by the wave at the antinodes is very small for the amount of acoustic pressure that I was generating. Theoretically if you could generate a large enough amount of pressure it would start to push the plates away.

[LuluSweetThing]

nice work!
did you find a ideal frequency and amplitude and by using only this frequency you did the levitation? I mean was it necessary to use any sensor?

[Aran]

Not sure if you can answer my questions but this is very interesting to me... Do you know if any force is exerted on the two plates from the pressure of the sound? say it was tilted horizontally, and you put those balls there, would it just push them away?

[skm]

im doing a simular project for my uni, but i want to lookin in to using the science behind it, to see if i can in theory, on a larger scale. i was wondering how much would it cost to build an acoustic chamber? so i can have a visual aid, when i give my demonstration about the power of standing waves

[xiaohuang]

Hi, this is a really cool experiment. I'm thinking to repeat what you have done there. Right now I have a ultrasonic generator and speakers. I'm not sure what type of amplifier I should use. Could you please give me some advice? Thanks !

[chrismurray]

Thats ok, if you have any other questions just ask :)

[chrismurray]

@skm21 How big are you wanting to build it? and out of curiosity which university are you at?

[casseyclarke]

Hi, wow thanks, great video! Are you able to make a helmet that has nodes that produce ultrasonic standing waves? I am looking for someone who could make it. The ultrasonic waves would produce brain stimulation.

[chrismurray]

@blazing94 Can you elaborate on your statement?

[marjanvitorijoski]

where can i find any theory in pdf format ? Who can halp me for that. TNX

[skm]

@chrismurray72 not looking for anything big, prob simular to what you have, just want to have a visual aid when i have to do my demo. I am a maths student at staffordshire university