Steingraeber factory pictures,bridge agraffes & adjustable vertical hitchpins

[Ric Brekne]

Hi Robert

Wanted to get back to you with a few observations. 

Weinreich measured things in a real piano with the standard bridge pin 
arrangement.  I dont think it can be said that he isolated  string 
behaviour such that he could confirm one way or the other the question 
of whether a string will vibrate longer if kept vibrating in the 
direction of excitement or not.  In fact there are several bits that 
naturally enough probably have never been really looked at all all along 
these lines.

For example, one of the main points made in Weinreichs contribution is 
that the reason for the strings transition from vertical to horizontal 
direction is the impedance of the soundboard in both these directions... 
which is of course higher in the sideways direction... but far from 
absolute. (He ends his segement on vertical and horizontal vibration 
with an interesting comment about soundboard behaviour btw.)  
Anyways...  there are a couple things worth thinking about here.  If its 
the soundboard itself that is responsible, then the string still has to 
be adequately coupled to both directions of soundboard vibration for 
there to be a transition. Perhaps this is impossible to avoid if its 
coupled at all, I dont know and I dont think this has been actually 
checked out.  A lot of what seems obvious is taken for granted in this 
kind of thing... but you never know until you look.  It seems 
counter-intuitive to me however that there is no particular coupling of 
string to soundboard that can result in any different relative strength 
of coupling to either direction of soundboard vibration then any other 
type of coupling.  Could be I suppose... but then again... I dont think 
anyone has really every bothered to check this out. If coupling can play 
a role on the other hand, then the bridge termination becomes a tool 
with which to design in loudness and sustain characteristics along with 
other known parameters for this.  This fits in with both claims from 
Wapin and Stuart.

Cheers
RicB


Robert Scott wrote:

> Hi, Ric.
>
> In response to your query:
>
>> Someone mentioned something about a presumed vertical vibrational mode
>> enhancement being automatically something that would simply pump more
>> string energy directly into the soundboard and actually decreasing
>> sustain.  I would say that was rather premature stated.... tho I would
>> be delighted to see any science that backs that idea up.
>
>
> I think the research done by Prof. Gabriel Weinreich backs this up.  
> He carefully measured the amplitude of the sound as it decayed.  What 
> he found was that the decay was not a pure exponential as you would 
> expect if a constant fraction of the energy got siphoned off on each 
> vibration.  Instead he saw the amplitude decay at a higher rate at 
> first, and then settle down to a fixed lower rate.  The transition 
> from fast decay to slower decay coincided with the observed (by 
> optical means) transition between pure vertical string motion and 
> ellipical string motion.
>
> Robert Scott
> Ypsilanti, Michigan
>