coupled motion of piano strings

[Stephen Birkett]

Michael wrote (on the subject of coupled motions of piano strings):
> I have a transducer that collects the signal of the motion of the
> string excited by a grand hammer of an action model.  My device
> consists of a monochord with piano like terminations. The string
> passes by two copper plates each about three inches long.  The
> string [.....snip....]
> Since the plates are
> perpendicular to each other they have the ability "see" the string
> motion in two independent planes. [....snip....]
> After a few milliseconds the motion begins
> in the horizontal plane.  This horizontal movement delay is when the
> string moves after it has been reflected from the nearest
> termination
> point.  I can see that time delay vary as I change the strike point
> of the hammer in relation to the string. I can also detect differing
> decay rates between the two planes of motion. Thi s verifies some
> earlier work of Weinrich (1977 JASA, I believe).
>
You might like to check out the follwoing reference on this subject:
    F.L. Curzon, Classroon simulation of the coupled motion of piano
    strings, Am. J. Physics 52 (1984) 137-139
The author describes a contraption they built with an aluminum pipe
and some springs to demonstrate the `Weinreich effect' as they call
it...symmetric and anti-symmetric vibrations. Sounds like a
mechanical version of your experiement...would be interested in
seeing the results of your work. BTW the oringal paper by Weinrich is:
    J. Acoustical Soc. Amer. 62 (1977) 1474-?
There is also the Scientific American article [240 (1979) p94-?]

> I do plan to publish this when I polish up the experiment.  I need
> to eliminate
> some confounding errors, organize my data, and prepare a
> presentation.
>
How about video-taping your experiment.

> I do not plan to have it published in a scientific
> journal so it will probably end up in our "Journal".
>
Publish this somewhere at least...it sounds good?


Stephen Birkett (Fortepianos)
Authentic Reproductions of 18th and 19th Century Pianos
Waterloo, Ontario, Canada
tel: 519-885-2228
fax: 519-763-4686