This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Hi Alan et al., >> Ah, you were so close to naming it. It's called longitudinal = inharmonicity, When strings vibrate, they don't just go up and down, as = sketches of string motion are drawn. They move in all directions, very = complex. Simply put, the strings in question are some combination of = damaged, poorly made, dirty, corroded, stretched out, or just old. The = motion in one or more directions is hampered in some way so the string = harmonics are "fighting" each other, i.e., not matching up, going out of = phase. Very cool. Now I know the name. <smile> Just to expand on this = concept, if the impulse (i.e. hammer blow) delivered to the string has = both vertical and horizontal components, and if the vertical and = horizontal components are not simple scalar translations of each other = (i.e. that the horizontal force is a fixed multiple of the vertical = force, such that they could be resolved as a simple, unidirectional = impulse at an angular direction -- highly doubtful), then the initial = horizontal and vertical spectra would have different relative = representations in the different harmonics (partials). As a result, the = resultant angle of vibration would differ between harmonics. (Think = about it.) Now, considering the inharmonicity of the string, the = phasing of the different harmonics would drift. As they drift, angle of = vibration at any given position of the string would also drift, i.e. = being the sum of the vibrational components from each harmonic, which = arguably are set at different angles in an imperfect system. Add to the = cocktail that nonlinearities in string behavior would result in the = gradual transfer of energy from lower frequencies to their harmonics in = the *same* vibrational direction as the lower frequencies, with those = frequencies summating with the (slightly different frequency) harmonics = at different vibrational angles, thus causing a shift in the angle of = the resultant vibrational component. YOW!! WOW!! This could make a = person's brain bleed! ANYWAY.... I think the answer with regard to the non-yowing Bosendorfer = vs. the other yowing pianos is probably the absence of horizontal = components in the initial impulse to the string. That is, (1) the = hammer is better balanced on the shank, such that the shank doesn't = twist when set into motion; (2) the hammer's center of mass moves = perfectly in-line towards the strike point (not with respect to the arc = of it's swing); (3) the centers are tighter, resulting in less play; (4) = the hammers are more uniform and/or less grooved, such that the string = is not "tapped" slightly to one side; (5) other factors that you piano = techs would know better than I would. Basically, it's a more precise = motion that delivers, say, a 99.5% vertical and 0.5% horizontal blow, = even after all the twisting and flailing that the hammer undergoes en = route to the string. Perhaps the extra care in manufacture? Perhaps = luck of the run? Perhaps it's also partially related to the use of = hornbeam, which I recall flexes less??? I remember taking lessons as a teen on my teacher's concert Bosendorfer. = Cool piano! I think she loved that piano like a child. Still, I = confess I didn't enjoy it as much as a beat-up Steinway B in one of the = practice rooms at my alma mater. The piano didn't look like much, but = it sang beautifully -- even if it might have yow-yow'ed a bit! Peace, Sarah ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/1f/d7/24/0a/attachment.htm ---------------------- multipart/alternative attachment--
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