What happens to the fundamental?

I built a sealed kundt tube 200 cm long with drivers on each end to ‘see’ AND hear resonance, etc..

. It goes nuts at 172.8hz and forms these shapes.. (the video is super cool looking in slow motion!) the other freqs dont (Barely) form any shape ? What’s up with 86.4, it doesn’t form the ‘stripe shapes’ within the sine wave formations of gathered vibrating styrofoam beads?

I think I can email (?) or FB messenger the short video
 

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Kundt's tube - traditionally, you would have a driver at one end of the tube and the other end closed.

By the "stripe shapes", I presume you are referring to the "walls" or "striations" formed by the styrofoam balls.

1681679605881.png


Their formation appears to have something to do with the "acoustic streaming" mentioned in Wikipedia: https://en.wikipedia.org/wiki/Kundt's_tube

Apparently, the additional transverse stripes form in the antinodes, caused by the circulation of air between the wall of the tube and the tube axis.

https://www.ld-didactic.de/literatur/hb/e/p1/p1731_e.pdf

I'm not claiming to be knowledgeable about this phenomenon, it's just the little I've managed to glean from an internet search!
 
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