Trying to understand how a lossy termination results in a lower pitch, I imagine that there is an effective elongation of the speaking length due to the reduced rigidity of the drier wood parts in the cap and root of the bridge, and possibly the board, and that there is an effective shortening of the speaking length when those parts are made more rigid by the uptake of moisture. In other words, a less stiff termination is more likely to move with the vibration of the string and so the actual point of termination has to be somewhere behind the bridge pin. Tom Cole Ron Nossaman wrote: > > As to how pianos go out of tune, in general, with humidity changes, > there's not much to indicate that soundboard rise and fall has much > part in the process. There is empirical evidence that the bridge cap > is a more major player than we suspected, but likely still not enough > to account for what we hear. I think the pinblock is also a player, > but the one I'm liking more and more is Michael Jorgensen's > suggestion. A vibrating string, demonstrably, sounds at a lower pitch > with lossy terminations than it does with rigid ones. That would mean > that a typically high compression soundboard, though it won't rise > enough to appreciably affect the tension of the string, will stiffen > under constraint of the ribs and become a less lossy termination of > the strings (via the bridge). That would make the strings sound at a > higher pitch without significant geometry changes. How it reacts with > strings at different break%s, I don't know. I hope to set up some > reasonably sensible experiments some day to see if I can clarify any > of this. > > But for now, It ain't the soundboard rising and falling that's > changing the string tensions enough to produce the tuning changes we > see seasonally. There is still a lot pending. > Ron N >
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