Soundboard Vibration

[Robin Hufford]

Richard,
     I have not been able to access the entire article with the link you included in your post which I would very much like to do.  Is this the correct link?  It proceeds only to the abstract which you quote.
     I still urge the view that the principal transfer of energy  is not, as he suggests, transverse and would suggest that this is, again an assumption which has then, mistakenly,  been found to be verified by the discovery of such transverse motion at the bridge, a motion,  however,
which  has been induced by stress transduction and subsequent wave development as has been previously described.   The two appear, to my mind at least, to have been confused by the few experimenters that I am aware of,  who have actually addressed the question of soundboard behavior in
pianos.
     Quoting from this site:
     "The bridge of a piano is the place where two important components, the strings and the soundboard, meet and interact. The motion of the bridge is important for understanding soundboard vibrations and sound production. This motion is also central to the interaction between strings, and
to coupling of the different modes of a single string.......While the dominant motion is, as one would expect, perpendicular to the plane of the soundboard, the experiments show that motion parallel to this plane is also quite significant. Quantitative results for the in-plane motion are
presented, and its role in sound production is discussed. We also consider the implications for modeling of soundboard and string motion."
      Judging from that which  is available at this site no distinction is drawn between motion of the bridge whether in-plane or otherwise induced by a lifting up and pushing down of the board as suggested occurs by those who advocate such, and that of motion induced by  superpositional
effects of elastic stress fields,  that is wave development in the board which then carries the bridge.
     This is a critical distinction which, of necessity must be drawn for an accurate answer to this question, so long a source of contention here, to be found,  and is a beginning to a clearer understanding of soundboard behavior.  The few researchers I am aware of who attempt this
question, for example, Wogram, Suzuki and others, appear to approach soundboard behavior with an assumption that the cyclic loading of the pressurists is, indeed, the primary method of energy transfer, it being, apparently, so readily obvious as not to require real investigation, and move
on, as I have said before, to soundboard behavior.
     Perhaps, this investigator will be shown by material in the full article to have taken this into account, as I sincerely hope he has,   thereby having  demonstrated that he, unlike others, has actually understood the subtleties of this question and been able to answer it without having
been seduced and distracted  by the more readily apparent questions inherent in the larger aspects of soundboard behavior.  The full article may show this or it may demonstrate that, once again, another researcher has proceeded directly to these larger questions by way of assumption about
this first, subtle issue.

Regards, Robin Hufford

Richard Brekne wrote:

> Been doing some more reading on this and have the following offering to submit. Goes to the question of transverse / longitudinal string vibrational input to the soundboard / bridge assembly.
>
> >From a 20 page article... "Sound Production by a Vibrating Piano Soundboard"  (N. Giordano)
>
> Giordano is  the professor of physics and assistant dean of science at Purdue.
>
> "IV. SOUND PRODUCTION BY AN IN-PLANE FORCE ON THE BRIDGE
> It is well known that the blow of a piano hammer excites both transverse and longitudinal
> vibrations of the string [2,7]. 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."
>
> The whole article (in GS format) may be found at
>
> http://www.auditory.org/asamtgs/asa97snd/2pMUa/2pMUa4.html
>
> and takes the track that non transverse vibratory movement in sound production from piano soundboards  is more significant then previously thought. He also stresses that the subject matter has been subjected to such study in the past only by Susiki and Wogram in rather limited projects.
>
> Happy reading.
>
> RicB