[Phys-L] Re: An Interesting reflection phenomenon

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 22:29 -0500 4/17/05, Brian Whatcott wrote:
> Here's the $64 question: the nodes as you observed them: which ones
>   were they? a breathing mode? a quadrantal mode? Higher?
>
> I am going to suppose that you possibly saw a mode that was
> bilaterally symmetrical, associated with a near parallel light beam
> path to you from the drum heads.
Interesting questions. Unfortunately, I don't know enough about the
various modes of a drum to answer the question of which modes they
were. There certainly was some symmetry to what I saw, but I
attributed it to the natural symmetries of the drumhead vibrations. I
could not directly see the drumheads, since my view of them was
blocked by music stands right in front of them, and the row of
trombonists who sat in front of the drums. All I could see was the
reflections, so I don't think I was seeing an interference pattern
between the drums and their reflections. However, is was probably 50
feet from the drums and sitting slightly above them. The angles were
such that the reflections appeared to me to be oriented in a vertical
plane--the drumheads appeared very nearly round, and not elliptical
as they would have had their apparent orientation been horizontal in
the reflections.

I can't rule out your suggestion, but since I didn't have a good view
of the drums themselves, I suspect it wasn't the case.

Hugh
--

Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

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