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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.
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