Sound waves(The behavior of soundboards)

[Charles Neuman]

Ron Nossaman <RNossaman@KSCABLE.com> wrote:
> http://www-ccrma.stanford.edu/~jos/waveguide/Dynamic_Terminations.html
> ...When a traveling wave reflects from the bridge of a real stringed
> instrument, the bridge moves, transmitting sound energy into the
> instrument body.

Here's another one along those same lines:

   http://www.physics.purdue.edu/piano/

>From an article at that site (title and abstract below):

"It is well known that the blow of a piano hammer excites both transverse
and longitudinal vibrations of the string [references are given]. The
transverse vibration leads to a force on the bridge which is directed
perpendicular to the soundboard, and thus to sound, and this sound
generation has been the main subject of the present work. Longitudinal
string vibrations will yield a force on the bridge which is along the
string direction, i.e. parallel to the plane of the soundboard. This force
will also drive soundboard vibrations which can produce sound, although
one might expect that the amount of sound generated by this mechanism will
be small. To the best of our knowledge, generation of sound via this
mechanism has not previously been studied."

Here is the title and abstract of the paper, FYI:

Sound Production by a Vibrating Piano Soundboard  (N. Giordano)

The generation of sound by a piano soundboard is investigated
experimentally, through measurements of the sound pressure, p, and the
soundboard velocity, vb, produced in response to a force applied at the
bridge. Results for the ratio p/vb as a function of frequency, for forces
applied perpendicular to the soundboard at different locations (i.e.,
driving points) on the bridge, are presented. At all locations, p/vb is
largest at frequencies of order 1 kHz, and falls off below a few hundred
Hz and above about 5 kHz. A few results obtained with the force applied
along the string direction (i.e., parallel to the plane of the soundboard)
are also described. These results are compared and contrasted with
previous experiments, and with theoretical expectations. [Journal of the
Acoustical Society of America, vol. 104, p. 1648 (1998)]