<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> <title></title> </head> <body bgcolor="#ffffff" text="#000000"> Hi David <blockquote>Ric - This was one (just one) of the reasons I was so sad at not being able to be in Rochester. I hope Steve Birkett does make the DVD available. </blockquote> Im sure he will. <blockquote>You said a few things: >the initial pulse and reflections look a bit more like a Gausian >[sic] wave then a straight traveling wave </blockquote> To begin with... it should have been spelled Guassian... and I say this only because of an applet I ran into once that struck me as very similiar to the wave action I see in Birketts high speed photography.  The initial pulse  looks sort of like a small upwards facing loop in an otherwise straight string. It travels along the wire and hits the bridge whereupon the loop reverses polarity.. i.e. faces downwards. But the thing is it really doesnt look like the amplitude of the loop ever goes below (or perhaps only barely below) the initial string line.  If you have a gander at the following page :     <a class="moz-txt-link-freetext" href="http://www.kettering.edu/~drussell/Demos/reflect/reflect.html">http://www.kettering.edu/~drussell/Demos/reflect/reflect.html</a> , neither the absolute soft or hard examples seem to fit... rather something inbetween seems to happen.  Of course one would have to examine the high speed photography much closer to be sure.. but it appeared convincingly enough to me that the reflected pulse highest amplitude did not go below the origional string line until the pulse had traveled quite a ways back across the string. By the time it got to the agraffee... it was all below the string line and the same thing happens again in reverse.  If true.. it means that the pulses force on the bridge is in an upward direction, and the restoring force downwards never pulls the soundboard below its origional height.  Only after the traveling pulse dissipates into a standing wave does there appear to be an upwards and downwards force on the bridge that is equally above and below the origional string line. <blockquote>You also paraphrased Birkett along the lines of  "namely that if you can't measure it or photograph it...".  Well, I've been wondering about something for quite some time, but haven't known exactly how to pursue it, though the information is probably right under my nose, (as in previously discussed on this list).  How does wire look (and act), molecularly, at rest, and how does that molecular structure and behavior change as tension is applied, and as it approaches and attains breaking point?  On what level does the behavior of the wire change as a response to material imperfections (in fact, how uniform is the molecular structure of piano wire?brand to brand?) or to physical distortions (bend / crimp) or to the physical process of termination?  Did Birkett speak of making any observations along these lines? </blockquote> No... he didnt get into that kind of stuff at all... Tho I suppose the jist of what his point was holds just the same.  I'll let him speak for himself on the matter tho.  I just understood his point to be that all the math models and theories in the world are and never will be declarations of truth or fact.  If you can observe something on the other hand... well its rather hard to dispute what you can measure... as far as that goes.  <blockquote>Lastly, I'm not sure what you mean by: >  I am wondering at this point whether or not the <<definition>> or > focus of the termination at the bridge is what is at work here. Sorry to have missed you on your trip to the states, and I hope the cinematic references were not too obscure (or too obvious) for you.  Any of you. David Skolnik </blockquote> I just meant that the exact conditions and angles of the semi clamped termination at the bridge in themselves could perhaps influence significantly the efficiency of the reflected pulse.  The pulse will hit the bridge and some of its energy will be used by the soundboard/bridge assembly in making the sound we hear... some of it will be reflected back down the string for further use... and some of it will get lost due to various things like friction.  Perhaps there is something about the angle of initial reflection that touches directly upon how much gets lost ? Just musing... as usual you see.  Better ?? :) btw.. it would have been cool to have bumped into you too !  It was great fun meeting so many pianotech folks this time around. No exceptions ! Cheers RicB </body> </html>