Sound waves(The behavior of soundboards)

Richard Brekne Richard.Brekne@grieg.uib.no
Fri, 04 Jan 2002 00:01:04 +0100


Ron Nossaman wrote:

> >On the one hand it was recognized that the bridge
> >does
> >indeed get moved physically up and down to some degree by the strings and
> >this to
> >some degrees moves the soundboard.
>
> To which degree was that, other than affirmative, and what other degrees
> were offered and explained? Note the word "explained" here.

To "some" degree. I offered no further restatement of others posts and see no
reason to do so now as whatever degree ...absolute or otherwise is irrelevant to
the point that I was making..namely that a concession was made as to bridge
movement... and nothing else. If you  want further explanation then I will let
those who made those comments speak for themselves... or you can re-read these
posts yourself.

>
> >On the other hand it was also conceeded that
> >completely immobilizing the bridge, inhibiting this physical movement,  leaves
> >some sound to be heard from the board.
>
> Which is also easily enough explained by the fact that the strings will
> shake the whole structure from the other end too. The plate, pinblock, and
> rim will be moved by a vibrating string, albeit less so, just like the
> bridge would be. NOTHING IS ABSOLUTELY RIGID, and A SMALL MOVEMENT IS NOT
> NO MOVEMENT AT ALL. And while you may be able to hear the result, it will
> hardly be quite acceptable as piano sound.

That's not a qualified explanation Ron. You simply are making an unsupported
declaration. On what basis do you conclude that any sound heard in this
hypothetical situation is from the string vibrating the rest of the system in a
transverse fashion and not because of compression waves transferred through the
bridge ? Especially in light of the experiment McFerrin describes which quite
clearly validifies that compression waves can and do indeed cause sound to emanate
from the sound board in this fashion. And by your own logic Ron... some
influence.... no matter how small... is significant, though you seem say that if
its some then it must be all.  If the resulting sound is there then it is a
component of the sound we hear, and without it what ever is left from the bridge
movement component (assuming that is real) would no doubt suffer as well.

>
> >Take for example the rock in the pond illustrated presented in this
> >discussion to
> >clarify this buisness about soundboard ripples. A rock is dropped into the
> pond
> >and we see surface ripples. Brilliant... but what was completely
> overlooked was
> >the fact that there are a lot of things going on under the surface at the same
> >time.
>
> What has apparently been completely overlooked is the blanket on the
> clothesline analogy, which was presented as a better model, and has nothing
> under the surface at all to confuse anyone. That was covered.

So was the ripple, but I will finish re-reading all this in the next couple days
and look out for your clothesline analogy.

>
> >In any case... it would seem to me that neither of the theories presented is
> >sufficient alone to be the basis of any good working model of the panel. Tho
> >either may have their uses as a particular perspective.
>
> I sure couldn't tell, since I never did get an explanation of how the other
> theory was supposed to work other than repeated restatements of the theory
> and the insistence that it was correct.

Sounds about what I have heard from your camp as well to be honest, but I never
said the other theory was correct either, I just said it hadn't been refuted at
all, and that some of its claims have been shown to be true... which is about
exactly as much as I said about the theory you propose. I have also pointed to my
view that both have problem areas which need to be resolved.

> Perhaps I missed it. I didn't read
> a single observation or demonstration that wasn't easily enough explained
> with conventional physics.

Excuse me Ron... but this is a complex system. Whatever you mean by the phrase
"conventional physics", this is not an "easy" system to describe. And I haven't
seen that you have managed to explain away or refute satisfactorily much at all
about the other side regardless of the complexity of the physics. And I see less
now that McFerrin seems sided up with them, dated though his writings may be.

> Perhaps I missed that too. I also seem to have
> missed any counter argument based on published physics that refuted any of
> my models or explanations.

I have never said your models or explanations were refuted... in fact I said the
opposite. Even in light of the problem areas I pointed out I underlined this
fact....The presence of unresolved issues with a theory isn't the same thing as
saying its refuted.

> You've read these posts over and over. Perhaps
> you can tell me where this compelling evidence in support of the opposing
> theory appeared in these posts.

I didn't say there was, I said that I saw nothing about it that would make me jump
all over it and condemn the whole thing, and I also said I saw problems with it.
Exactly the same that I have said about yours. I also said that I thought both
proposals had some merit and that the real answer to this question probably
includes elements from both these ideas and probably more that we haven't even
thought about yet. But when you first mention it, I don't see anything
overwhelmingly compelling about your theory either.

> I can't see that they have made any case
> whatsoever much less left room for lingering doubt but, as I said, I might
> have missed it.

I know your view of the other theory already.  I am, perhaps due to my own
ignorance or perhaps due to some other attribute, a bit more open to pondering
differing ideas.... Funny how McFerrins statement about transfer of energy from
strings through the bridge is nearly, if not out and out, identical to Robins
though... I mean if this theory of his is so stupid and all..

>
> Ron N

Jimmineess.... this isn't a passionate thing you know... Wasn't it Rodney King who
said something about everyone keeping their pants on or something ? :)


--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no




This PTG archive page provided courtesy of Moy Piano Service, LLC