On Jan 11, 2011, at 4:10 PM, Ron Nossaman wrote: > With anything vibrational, stiffer raises pitch, more flexible lowers it. > Adding mass lowers pitch, removing some raises it. While it is true that stiffer raises pitch, more flexible lowers it, that does not necessarily directly correlate to adding or removing mass. It depends on where you remove (or add) the mass. Removing material from the base of a tuning fork makes it more flexible, lowering the pitch. Removing it from the ends of the tines makes them relatively stiffer and sharper. In both cases mass is removed, to opposite effect, regarding pitch. More to the point of Shoenhut's tone bars, this type is sounding body is a bit more complex. The pitch of marimba or xylophone bars can be raised or lowered by only removing mass. In fact, the frequencies of their second and third partials can be controlled relatively independent of the fundamental, all by removing material at strategic locations. With these types of tone bars, the portions of the bar that extend beyond it's fixed points serve as counterbalances to the vibrating length between the fixed points. Removing material from these end segments have the opposite effect of removing material from the segment between the fixed points. It has to do with shifting the center of gravity, one way or the other, from the termination points (fixed points) of the vibrating body, which can be done, either direction, within limits, by only removing material. In an effort to get the second and third partials just right, and erring in pitch measurement due to heat generated by removing material, it is easy to fluctuate back and forth between raising and lowering pitch to the point that the bar is so mangled that you just have to throw it out and start over.DAMHIK! George F. (Frank) Emerson -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20110113/f8df30ca/attachment.htm>
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