Re: coffee mug oscillatory modes

[Mark Sylvester <msylvest@SPIN.IT>]

Pretty good! I read this just as finished my morning coffee, emptying the
high-quality mug that I bought at the Roentgen Museum last summer. Tapped
lightly with a plastic ballpen, the mug produces the same note (to my ear)
at the N, S, E, W points, but at least a whole tone higher (by ear - to be
checked with fft shortly) at the NE, SE, NW, SW points.

Mark

At 13:42 02/06/99 -0700, Leigh Palmer wrote:
> While we're on the topic of cylinder wall resonance I thought I should
> mention a simple demonstration a colleague at Oxford, a chemist, showed
> me. Place an empty cylindrical coffee mug on a tabletop with its handle
> pointing north. Using a spoon handle or other hard metal object tap the
> south edge of the lip of the cup sideways and listen to the note
> produced. Now try tapping at different azimuths, notably the cardinal
> points and the points midway between them (e.g. SW, NE, etc.). If you
> find a good mug you will hear a difference between the cardinal points
> and the midway points of as much as a semitone, a frequency difference
> of more than five percent.
>
> The explanation of this phenomenon is easy and elegant. I won't spoil
> the discussion by giving it here; I want you to do the experiment! As
> Ron will point out, this is an example of what is called "symmetry
> breaking" elsewhere. I bring it up here because the oscillatory modes
> of a beaker are the same, and they exhibit the same symmetry breaking
> phenomenon (to a lesser extent) as the coffee mug. Incidentally, we
> too break both beakers and wine glasses here at Simon Fraser. Sometimes
> we use sound.
>
> Leigh
>
> (The Oxford chemist is Peter Hore. His wife, Julia Yeomans, an Oxford
> theoretical physicist, may have helped him a bit; I don't know.)
Mark Sylvester
United World College of the Adriatic
34013 Duino TS
Italy.
msylvest@spin.it
tel: +39 040 3739 255