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Flight of Sound

"sounds" like a good idea
  [vote for,

I have another idea for an engine that can allow levitation. This engine would rely on sound waves to provide "thrust", much like when you turn a speaker on full volume and objects can move to the resonance of the sound. I imagine a sound wave would be necessary that is outside the human range of hearing (don't want to deafen everyone !). The sound emitting engines would be attached to the underneath of a craft. The louder you turn up the sound the higher you fly !! "sounds" easy. What do you think ?
Lancaster Bomber, Aug 13 2002

(??) Formation and Levitation of Unconfined Droplet Clusters http://ncmr04610.cw...n1999/papers/61.pdf
Warning: It's a .PDF file. [phoenix, Aug 13 2002, last modified Oct 04 2004]

Soliton waves http://www.ma.hw.ac...solitons/press.html
Propagation phenomena [8th of 7, Aug 14 2002, last modified Oct 04 2004]

(??) Acoutsic Streaming Microjets http://www.eecs.umi...EMS01_resonator.pdf
A paper on experiments with acoustic streaming for micro-propulsion. [planckZero, Aug 21 2002, last modified Oct 04 2004]


       Hmm... and what effects would said waves have on other objects they encounter? My windows are not liking this idea.   

       Just because your rearview mirror vibrates when you crank up the bass does not mean this is an efficient propulsion system..
Mr Burns, Aug 13 2002

       Additionally, speakers vibrate while staying in one place, so any "propulsion" would be cancelled out when the speaker travels in reverse.
Mr Burns, Aug 13 2002

       The air affected by sound waves vibrates back and forth, strictly limiting forward thrust, I would have thought.
DrCurry, Aug 13 2002

       Using acoustic energy for propulsion wouldn't be as easy as flipping the switch on a giant power amp and speaker setup... as DrCurry noted, the back and forth motion of the vibrating element creating the sound waves would not create forward momentum. You'd be left looking for non-mechanical means to generate the sound wave, and at that point it would be less efficient than other established means of propulsion, if it would work at all.   

       The paper phoenix cited deals with creating standing acoustic waves to confine particles at nodal points... hardly directly applicable to propulsion. The particles "move" to the nodal points because they are the areas of least energy. Trying to create a propulsive force by adjusting the position of the nodal points and using some kind of reaction mass would likely be grossly inefficient.   

       DrCurry... actually there is a phenomena called "acoustic streaming" where by a net movement of the conducting medium in the direction of wave propagation can be observed. The momentum produced is proportional to the wave energy, but is still relatively small. It's not at all clear that this effect could be scaled up to the energies necessary for practical propulsion (other than microcraft) in any reasonable way.   

       However, I do believe that it IS possible to harness acoustic energy for reaction propulsion... I'm just not sure exactly how yet.   

       Incidentally, one way to solve the problem of the vibrating element is to have it only "vibrate" the air in one direction, moving as much air as it can as quickly as possible. It would then look a lot like a propeller ;-)
planckZero, Aug 13 2002

       There are some theoretical indications that ideas such as this may not be entirely impractical (see link on Soliton waves) so this is not a WIBNI, but it is beyond the current capabilites of engineering.
8th of 7, Aug 14 2002

       Set a screaming child in a public space and watch as the acoustic energy propels people out of that space.
bristolz, Aug 21 2002


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