What we have: Supposed that we have a loudspeaker-based ultrasonic levitator. including a low voltage sine wave generator, an amplifier and a loudspeaker + a metal plate and some clamp-stands +some small polystyrene balls to levitate.

Main idea: This levitator is designed to work at a frequency (or pitch) of around 25 kHz which is above the audible range of humans.

How can we determine how much will be the movement of small polystyrene balls?

Details about other variables:

  • The sine wave generator, generates a sine wave in the frequency range 20-30 kHz and an amplitude in the range 1-5 Volts (peak-to-peak).
  • The amplifier: 100 Watts, able to amplify old fashioned analogue signals.
  • The load speaker: high power tweeter or compression horn tweeter that works fine up to 30 kHz.
  • The object: small polystyrene balls with the range 1-2 mm.
  • Distance of plate and speaker: 50 mm.

This is very important that the exact movement of matters determined by mathematical formula.

The lab and real exp.

  • 2
    $\begingroup$ How can we determine how much will be the movement of small polystyrene balls? .... experimentally $\endgroup$
    – jsotola
    Jan 22, 2018 at 20:35
  • $\begingroup$ Thanks @jsotola , but this experiments can't repeat for each different value or the high range generators; so we decided to have a brain storm to find an equation for this problem. $\endgroup$
    – SM_SOF
    Jan 22, 2018 at 20:39
  • 1
    $\begingroup$ @SM_SOF How do you intended to verify your equation if you can't develop a repeatable experiment? $\endgroup$
    – vofa
    Jan 22, 2018 at 20:42
  • 1
    $\begingroup$ This seems to be more of a physics question. You do not give details on the generated field, but is seems to be a simple standing wave. For speed of sound 331,2 m/s and 25kHz, nodes are 13.2 mm apart, that's simply a division (speed divided by frequency). $\endgroup$
    – Andreas
    Jan 22, 2018 at 21:05
  • 1
    $\begingroup$ Maybe some sort of stroboscope in-phase with the speaker but with variable offset. The strobe should flash in combination with a video camera running at e.g. 120 FPS. Thus it flashes once for each video frame, but still with know phase from speaker. $\endgroup$
    – oldfart
    Jan 22, 2018 at 21:10

1 Answer 1


Thank you for your comments but we need an equation to find the exact amount of movement; I saw someones told about there will be no movement, I should tell as we experienced in laboratory actually it works and we noticed those variables we brought in the last section are influencing the distance between plate and polyester balls.

If any body else thinks it won't work, I upload the pictures of experience to make sure about it:




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