interesting wood article

[Richard Brekne]

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Farrell wrote:

> At the risk of  asking a question that has been asked a zillion times
> before...... Is there perhaps a fundamental difference in the way a
> piano soundboard vibrates compared to whatever on a violin vibrates
> from string movement to produce their respective sounds?

Since the point goes to the general acoustic properties of wood... I'm
not sure whatever differences in construction between various types of
instruments is at all relevant.

Is the piano soundboard moving more like a speaker cone (I realize most
soundboards are pretty far from that ideal) compared to the vibrating
front of the violin? I ask that because if piano soundboard movement is
closer to the speaker cone, we are strictly looking at a vibrating
diaphragm, and the ability of the soundboard material to "transmit
sound" is a mute point (pun intended). To the best of my knowledge,
speaker cones do not "transmit sound", but rather move as a single unit
at whatever frequency(s) is required to produce intended sound - paper
cones work well, but carbon-fiber or a number of other exotic materials
with greater stiffness-to-weight ratios than paper work better - but not
because the exotic cone material "transmits sound" any better, but
rather because the material moves more efficiently as it is driven by
the speaker voice coil - or in the case of the piano, the string.

Well.. all I can say is that number one.. I've never bought into the
idea that the soundboard functions strictly as a speakercone does, and
secondly... if wood can transmit sound at all... then speaker cone or
not... you cant overlook the...er.. transmission as it were..  Besides
... if the pianosoundboard could so easily be defined and modeled...
then we could have replaced the material with something else and
achieved exactly the same sound years ago.
 So my question is - is the speaker cone analogy more closely related to
the case with the piano soundboard and less so with the violin? No
relationship?

I personally would think the piano soundboard functions far less like a
speakercone then some would have it, and the violin functions more like
a speaker cone then purists in that camp would feel comfortable
admiting. Again, if fear this has been asked before - and if I've read
info on it, I guess that means I just haven't thoroughly understood it.

Its been done over a zillion times, and if people with all kinds of
fancy initials behind their names continue to dissagree on the subject,
I suspect there is good reason for that dissagreement-...., and I
certainly would expect to find continued disagreement in forums like
this one. And here's a question that may not have been asked before (and
maybe for good reason): "As wood gets older,.....and displays lower EMC
levels." Does it? Or does it simply become slightly less dense from
losing volatile components, and then simply carries less water in it at
the same EMC?

Well... I dont know... I'm just putting out information as I run into
it. This latest came from largely from teh Tampere University of
Technology in Helsinki, tho there are some other resources on the nett
where you can find similiar information. The fellow behind this
particular study was one Pertti Nieminen, Docent, Ph.D.  He's the guy
(grin... amoung others) you want to ask. Tho I will look through and see
if Hoadly has anything to say on the matter.

I just think its all interesting perspectives to read what different
researchers around the world come up with. I wish I understood half of
it as much as I should, and all of it more then I do... if you get my
meaning.

Cheers

RicB Terry Farrell ---
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html
http://www.hf.uib.no/grieg/personer/cv_RB.html


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