Helmholtz and Steinway

[Richard Brekne]

John Delacour wrote:

> At 9:51 PM +0100 11/18/01, Richard Brekne wrote:
>
> >Taken from the Conklin article you refer to below is the following
> >quote, which he basically says two or three times over in the case
> >on non wound strings. It seems to me that Conklins statement is in
> >conflict with your own about the termination points having no effect
> >on the horizontal mode JD. Otherwise how can Conklins statement that
> >it is the length of the speaking length that determines the
> >frequency of the longitudinals ?
>
> Well I'm as keen to get at the facts as you and others are, Richard.
> It is not going to be easy without some experimentation and it will
> take a while to set that up.  If anyone else, such as Stephen, has
> more experimental data on this topic, I'd lovree to know about it.
> You wrote, quoting from Conklin:
>
> >  "The longitudinal frequency of a plain steel string in a piano can
> >be changed only by altering its speaking length..."
>
> Since he produces no demonstrations relating to plain wire strings,
> it is quite possible that he would need to prove that this would make
> a difference if it did not alter the TOTAL length of the wire.  Nor
> are we told how these longitudinal waves are initiated, how they are
> affected by the relative tension of the wire etc.  He leaves more
> questions unanswered than he solves, though what he does show is
> interesting.
>
> JD

Another point to this is that we are talking about two aspects of these
longitudinal waves really... Their frequency chararacteristics, and their
abililty to propogate along the total length of the string.

I dont see that Conklins statement says anything about whether or not the
waves are impeded in any sense by termination points, but he does say
directly that their frequencies are goverened by the speaking lengths.
Seems interesting to me that the speaking length then could possibly be
determinant in its effect on the strings longitudinal frequency, while
haveing no effect (or almost none perhaps) on the movement of these waves
beyond the borders of the speaking length.

This would jive tho, with the statement made by one of you all about the
excitement of a longitudinal wave in one of the duplex lengths being able
to only excite its own fundemental and partials in the speaking length.
I am unconvinced that plucking the string in the example Ron gives is
neccessarilly the same as exciting the longitudinal mode, which would
perhaps explain why he doesnt get the same results from both front and
back duplex modes. I am not sure that this "plucking" experiment of the
front duplex has anything at all to do with longitudinal waves. In any
case most of what I have found about exciting longitudinal frequencies in
strings has to do with rubbing them... sort of like how one gets the ring
from a crystal glass to sound. This would mean that the plucking
phenomena then is explained by something else.

I poked around the nett last nite looking for something directly relative
to this but couldnt find much.



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