The Soundboard according to McFerrin

[Richard Moody]

Twas quoted     (from an outside source)
    "SOUNDBOARDS, AND OLD WIVES' TALES
There is no physical movement in the board, as you think of physical
motion. "

Of course nothing could be farther from the truth.  Touch a soundboard and
if you don't feel it moving I suppose no one is playing the piano.  I
suppose the penny on a soundboard rattling worse than a crack cannot be
moving because there is "no physical movement of the board"   The statement
would be truer if it read, "as I think of physical motion.

Longitudinal motion is associated with sound traveling in air, sound
traveling through water, sound traveling through a sold.   Transverse
vibration is seen when  strings vibrate up and down, causing soundboards to
vibrate up and down at the same rate.  The sb is a diaphram much like a
speaker cone.   As it moves it displaces air.  This displacement is then
longitudinal.  It gets into mathematical realtion between the speed of
sound, and the frequency and wave length of the particular periodic motion
called sound.   The string itself is moving no where near the speed of
sound.  (but I wonder how fast it does move?) but the sensation of tone we
call pitch that we perceive comming from the string soundboard combination
reaches our ears at the speed of sound.  This is illustrated I think by
McFerrin  in Fig.1-2 p9.  Now the way I understand it is that this motion
of strings (transverse) produces longituditional motion (of air) that moves
with the speed of sound.
    By the way he says on the same page that a longitudional wave can be
produced in a piano string "by rubbing a piece of leather with powered
(sic) rosin, then grasping the wire and pulling the leather lengthwise of
the wire.  A squealing noise or tone will be produced.  Now I might
challange that by way of experiment.  If the "squealing tone" happens to be
the same pitch as a tone produced by bowing and then again by striking then
in this case what he is calling longitudional wave is not the same as what
he describes below Fig 1-2. "these lines represent air particles compressed
by some vibrating object atht e left which has given them a shove to the
right."  The explaination is much longer.   It is possible a piano wire can
vibrate longitudinally which I think rubbing with a rosin rag might cause,
but this is not the same as longitudinal vibration as physists such as
himself descibe.

Or course what is actually happening in phyiscal reality is no way
dependent or affected even by conceptualizations such as above.  It is
intellectual (well mental then) activity (effort?) to aid understanding.
(whatever that is).   But if it somehow will enable me to produce an
instrument as good or better than a B then I will expend the effort.
=-=ric

"From a practical point of view the pianist or piano technician may
consider that he needs to know little or nothing about the speed of waves
traveling to and fro along the vibrationg string.  However, it is well in
any vocation to learn more than the minimum background knowledge about that
vocation."
---W.V. McFerrin
Formerely Associat Professor of Physics The colege of Emporia, Emporia,
Kansas Craftsman Member of Piano Technician's Guild