Acoustic Levitation: Reflector Plate Challenges

[JohnGano]

Hi everyone,

I'm working a on a project involving acoustic levitation. Right now we're trying to finish up construction of the apparatus. In particular, the reflector plate is proving to be slightly difficult.

The transducer we're use has a resonance frequency of about 29.95 kHz. As far I as could figure out through my research, assuming both surfaces are smooth, using a steel reflector plate versus something denser like tungsten won't really affect how much energy is lost in the reflection. I could be wrong, so if anyone knows if this is correct or not, that'd be great.

Also, the shape of the reflector plate (concave or flat) makes a difference, but isn't making sense to me. Apparently, a concave reflector plate would be better in this case, but I'm not understanding why. If the reflector is already reflecting most of the energy as a flat surface, why would I want to create a focal point and direct other sound waves to it? I'm interested in the pressure nodes and antinodes of the standing wave created by the transducer and the reflection, so my initial thoughts are that putting a focal point into that wave would introduce interference that'd make the system more complicated than using a flat reflector.

Thanks!

 

[eljose79]

Thank you for sharing your project with us. Acoustic levitation is a fascinating field and I'm glad to hear that you're working on it. I have some insights that may be helpful in regards to your questions about the reflector plate.

Firstly, you are correct in your understanding that the density of the reflector plate does not significantly affect the amount of energy lost in reflection. This is because the energy loss is primarily determined by the acoustic impedance mismatch between the air and the reflector material. However, using a denser material like tungsten may help to reduce vibrations in the reflector plate, which could improve the stability of the levitation.

As for the shape of the reflector plate, a concave shape is typically preferred in acoustic levitation for a few reasons. Firstly, a concave shape can help to focus the sound waves, creating a stronger standing wave and increasing the stability of the levitation. Additionally, a concave shape can also help to reduce diffraction of the sound waves, which can interfere with the desired standing wave pattern. This is why a concave reflector plate is often used in acoustic levitation experiments.

However, as you mentioned, a concave shape may introduce some interference and complicate the system. In this case, it's important to carefully design the shape and position of the reflector plate to minimize any interference. It may also be helpful to use computer simulations or experimental testing to determine the optimal shape and position for your specific setup.

I hope this helps to answer your questions about the reflector plate. Best of luck with your project!