Hi Alan, hi Bruce. In my understanding up till now, the inharmonicity in piano wire is due to the metal stiffness at the attach points. At the attach points (whether they are moving (bridge pin) or not (aggraffee)), the metal of the string ha to bend in order to let the string vibrate. In fact, the string bends all over its length, but at the attach point it is the most critical. For lower harmonics, the ample movements of the string have more energy to bend the metal at the attach point, but for higher harmonics, the smaller movements of the string have less energy for that, and so there is a larger portion of the string at the attach point that will stay unaffected by those frequencies, so the string, at high partials, acts physically as if it was shorter (you have to subtract of the speaking length at those frequencies the portion of string that doesn’t vibrate at those frequencies near the attach point). That would be the reason why higher harmonics are sharp against their ideal theoretical (following Pythagoras) value : they actually ride a shorter speaking length. And then, there is the complex role of all the rest of the piano, communicating with the string via the bridge and the aggraffees (or capo) and making the whole shebam even more intricatedly complicated. Anyway, for a same speaking length, inharmonicity decreases as tension increases (hear the bell like sound, very inharmonic, when you release tension in a string). How this relates to that, I can’t imagine clearly. I would at first think that higher tension in the string would increase even more the difficulty to bend the string at the attach points. Anyone on this ? Of course, it would not be the first time that my understanding proves wrong, so it is subject to change without notice. I would be happy to read another better explanation, or the same but better said, or another but better said, or any for curiosity. Best regards. Stéphane Collin. From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of bppiano at aol.com Sent: vendredi 6 février 2009 6:22 To: pianotech at ptg.org Subject: Re: [pianotech] inharmonicity in piano wire The question needs to be referrenced to a piano wire at rest and a piano wire in motion. When a piano wire is in motion the actual tension of the wire flucuates from a position of rest to its maximum tension before it reverses direction in its wave loop times the number of partials counted. I imagine that as the part of the wave slows down before it reverses is the determing factor for the enharmonicity. I know that sounds like alot of words that poorly describes the myriad of actions that occur for every string that sounds as a part of a piano. But, it clearly frames it in my mind. I'm sure a pictoral representation would make it alot clearer. Bruce Pennington -----Original Message----- From: reggaepass at aol.com To: pianotech at ptg.org Sent: Thu, 5 Feb 2009 9:32 am Subject: [pianotech] inharmonicity in piano wire List, I just received a query from a science faculty member at the art institute where I work. He asks how can it be that partials of piano wire are sharp of what they "should" be? I told him that my very pedestrian understanding is that this phenomenon is due to the high tension of piano wire up to pitch, but that is just me repeating what I have heard "somewhere." Is this response even close to being correct? Any further clarification as to why this is would be much appreciated all the way around. Thanks, Alan Eder CalArts _____ Carnations mean admiration, Tulips mean love - what do Roses mean? <http://shopping.aol.com/articles/2009/02/02/flowers-by-meanings/?ncid=AOLCO MMshopdrspwebf0001> Find out now! _____ Get instant access to the latest & most popular FREE games while you browse with the Games Toolbar - Download <http://toolbar.aol.com/games/download.html?ncid=emlweusdown00000026> Now! -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech_ptg.org/attachments/20090207/f19db29d/attachment.html>
This PTG archive page provided courtesy of Moy Piano Service, LLC