Re: [Phys-L] Resonant One End Closed Tubes

[bernard cleyet <bernard@cleyet.org>]

Try gluing an O ring (rubber band) to make a good seal.

> On 2025/Apr/01, at 16:56, John Denker via Phys-l <phys-l@mail.phys-l.org> wrote:
>
> I'm surprised. I don't have much of an idea, but here are some
> partially-baked thoughts:
>
> Given that the water works and the wood does not, the problem
> cannot possibly be the wood per se. It has to be the gap between
> the plug and the tube, and/or the felt in the gap.
>
> -- Felt is widely used in musical instruments to *absorb* sound.
>
> -- Even a small gap, tiny compared to the wavelength, can absorb
> a lot of sound. Remember the old-style acoustical tile, with an
> array of small round holes?
>
> -- When the Q is high, it doesn't take much dissipation to lower
> it a lot.


On 4/1/25 15:53, Zeke Kossover wrote in part:

> So, I want to make a one end closed, one end open resonator with an
> adjustable plunger. My design is a wooden plug cut to fit the tube with a
> small wrapping of felt to let it slide. It works okay, but not nearly as
> well as the two ends open version or the one end open version and water.
> I don't understand why. Anyone have an idea?   

OTOH  try with the felt removed.  

I foolishly tossed turn of the century Kundt’s tubes with similar plunger and sound source a brass rod using a resin impregnated cloth.  

The plunger worked fine.  I think it was a brass disk, the tubes glass.  

bc  …  one more thing he regrets,  and very curious, as to the resolution of the problem.  

I’m too busy preparing for my FTIR, evanescent wave measurement, ** 1/4 wave plate, etc. X-band demos at the next NCNAAPT meeting.