IF YOU WANT TO KNOW THE TRUTH, STOP HAVING OPINIONS! In a message dated 02/19/07 15:37:29 Central Standard Time, davidskolnik at optonline.net writes: Ric, Paul, & All - Shooting from the hip, so to speak. I've been accurately (but well-meaningly) chastised in the past for not actively trying to find the answers to the questions I ask. I'm coming to accept that answers are not my roll. Perhaps something to aspire to. In any case, I'll pick through Ric's post below and refer to one item of Paul's. For the sake of space, I'm deleting all but the specific quote, so it would be necessary for a reader to access the original post to fully understand (if that ware possible)' At 06:41 AM 2/18/2007, you wrote: Hi Paul. Jim Ellis's article from way back. Can you better identify the source? Now I've got to do footnotes? I honestly will have to research the source. Ric, can you help me (us)? The problem with fitting a loose pin into this as something that <<directly causes>> false beats is that one attempts to go back to Jim's article... define the pin as the pendulums <<support>> and as such must claim horizontal movement of the pin as being the culprit. This gets problematic immediately. Jim himself denies that (stricktly) horizontal movement of the pin.. or that any in phase movement by the termination in any /particular/ direction at all is at root. In phase movement at the termination occurs in all directional planes of string vibration. He cites general springyness of the termination as a whole, tho is the first to go along with the idea that bridge pins can be a contributing factor in the general condition. I also wonder about the sidebearing of the string in this picture... it would seem to me that even if a loose pin was involved.... the least likely direction for in phase springyness would be the horizontal exactly because of the side bearing the string has. I haven't yet finished Jim's book on longitudinal waves (I'm working on it whenever I'm stuck in traffic or, oh, never mind), and perhaps I'll find that my preliminary visualization is completely misguided, but it seems that in the longitudinal forward and back direction, the pin could act as a pendulum and would be less inhibited by side bearing. Would the pin act as a pendulum per se (albeit oscillating) as much as the contact of the pin and string would redefine the bearing, fulcrum, pivot point of the pendulum? Even so, where does the beat come from? There would still be only a single varying frequency instead of two interfering with each other, yes? Quoting from Paul, albeit from a post that seems to come from Ric, Ric, I'd urge you to look at cycloidal pendula as an interesting and maybe contributing factor with "springiness"; cycloidal pendula are another class of pendulum where the "termination" is not a pivot with a bearing but one or more curved surfaces on either side of the period of the pendulum which foreshorten the period as the pendulum swings in contact with the curvature--can you see the picture of the string and bridge pin here at all?). Paul - Interesting idea, though I haven't yet checked the math...don't wait up for me...but, conceptually, I question this as a factor, for this reason. From the diagram I looked up, I would say that, for this to be an issue, the string would have to be flexible enough to comply with the curved profile. In fact, we know (?) that, at that point, the string's stiffness is already contributing otherwise, as inharmonicity. It doesn't seem you can have it both ways. In any case, if the cycloidal model does apply, it would do so generally, not specific to real/false beats. I'm glad you question it as a factor, since I do, too! I only suggested it as possible complication. I would say that the question mark you have after "know" is entirely appropriate; we don't know that the string stiffness is the or the only contributor to inharmonicity; perhaps the cycloidal pendulum effect and the foreshortening of the string is also a cause of inharmonicity, and that the variations in string length as it curves and contacts the pin variably and variously might also be factors in "false" beats. I can also imagine in a damaged (notched) pin, the variations of contact of the string with the pin. Physically impossible because of string stiffness? Maybe. Worth examining? Maybe. Another thing. While you may be correct about the real/false semantics, I'd hold off on pressing it, at least until you've found the cure. Otherwise we could solve the whole problem right now by renaming it "vibrato". Problem solved! Not really since a vibrato is a vibratory system (voice) producing a single pitch of continuous variation rather than a beat resulting from interference between pitches which leads me back to yadayadayada...:-). My original point was the possible confusion and misleading nature of the use of "false" which if we say is "real" then it leads us to an analysis of frequency interference (real beating). I don't mean to press it but to become a nag about it! We do need some clarity of language; whether this is the clearest language is still moot, but I offer it as a talking point. A while back, Stephen Birkett had been actively seeking ideas for experiments to perform. I've been meaning to go back and look at what was proposed. In fact it may have been on CAUT (can I say that here?). This subject would seem a likely candidate, though problematic. In order to deconstruct the condition, he would first have to create it, in a lab setting, or else bring in field examples for forensic analysis. CSI-Waterloo! Maybe its a bit like synthesizing vs. sampling. What do I know? An alternative might be to develop a standardized set of tests and observations which interested techs could perform in the field, which could provide a statistical base. It would have to be mostly non-invasive observation and testing, since time and opportunity would not always allow for such things as changing strings or removing bridge pins. Long enough - David Skolnik Then there are some empirical facts that simply cant be ignored. Purely from a statistical standpoint there is really no identifiable correlation between the occurance of false beats and loose bridge pins. Way to many cases where the opposite happens... way to many cases where the same false beat occurs when pins are actually tight. Then there is also this famous <<test>> with the screwdriver. Why does pressure with the screwdriver actually cause the false beat to start up again and speed up with more pressure when you've first put enough pressure on the pin to quite a false beat ? Why does the application of mass to neighboring bridge pins or back side pins also (sometimes) affect the presence of a false beat ? Strikes me that the whole presently and popularly accepted idea that bridge pin is /thee/ support for the string and that it /causes/ false beats is a pretty large oversimplification of the whole thing.... likely based on an equally over simplifed interpretation of articles like Jims. And as is very common in our trade the collective we jumps on the wagon declaring a new (and just as magical as any previous) Truth . Viola ! For my part.... I'll keep adding CA in appropriate circumstances... because it does help... (another discussion entirely :) )... but I'll also keep wondering about what the heck is really causing false beats. Clearly the loose pin thing is to thin. Actually... when it comes down to it... the recessed notch bit seems much more likely as it allows the string itself to have a partial vibrating in several planes at the same time at different lengths... the bridge pin doesnt need to even get involved here. For that matter... string imperfections at or very close to the termination can cause a string internal springyness that could be at root. The whole thing needs IMHO a lot more looking into before any definitive explanation is available. Cheers RicB Ric: What has always struck me about that particular mythology is the variability of beat speeds in real (false) beating. Attributing it to loose bridge pins would lead us, no?, to believing that the loose bridge pin is moving in some way in the bridge pin hole, wandering in some oscillating manner that would create a "countable" beat, sometimes as slow as one beat per second, and certainly much faster in most instances, but still regular and countable. I share your skepticism, and return again to some length differential being created in the speaking length by way of termination deterioration, particularly the notch part of the termination creeping forward in the curve of the notch and creating a separation from the ideal simultaneous contact of the string at pin and bridge top. This is an old can of worms, I know, but maybe worth revisiting. Paul IF YOU WANT TO KNOW THE TRUTH, STOP HAVING OPINIONS! -------------- next part -------------- An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/20070219/e62aaacb/attachment.html -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: image/gif Size: 1499 bytes Desc: not available Url : https://www.moypiano.com/ptg/pianotech.php/attachments/20070219/e62aaacb/attachment.gif
This PTG archive page provided courtesy of Moy Piano Service, LLC