<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style></style></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1>Something that seems to get lost in these demonstrations—or, more accurately, ignored—is the fact that we really don’t want resonances of this type present in the real piano soundboard. Indeed, I’ve spent some amount of thinking and “empirical” design time—i.e., trial and error—trying to figure out how to minimize strong resonances in piano soundboards.<o:p></o:p><o:p> </o:p>ddf <o:p></o:p><o:p> </o:p><div>Delwin D Fandrich<o:p></o:p>Piano Design & Fabrication<o:p></o:p>6939 Foothill Court SW, Olympia, Washington 98512 USA<o:p></o:p>Phone  360.515.0119 — Cell  360.388.6525<o:p></o:p><a href="mailto:del@fandrichpiano.com">del@fandrichpiano.com </a>— <a href="mailto:ddfandrich@gmail.com">ddfandrich@gmail.com</a><o:p></o:p></div><o:p> </o:p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>From: caut-bounces@ptg.org [mailto:caut-bounces@ptg.org] On Behalf Of Bob Hohf Sent: Saturday, May 12, 2012 7:14 AM To: caut@ptg.org Subject: Re: [CAUT] M&H crown device<o:p></o:p></div></div><o:p> </o:p>It's not that hard to investigate this sort of thing, which Dave Carpenter and I did a number of years ago while preparing a seminar for the Chicago School.  I don't have time at the moment to get into a long discussion of this, but will toss our grist into the mill FWIW.<o:p></o:p><o:p> </o:p>I made a toy soundboard, like the M&H device, on which we could gauge the amount of flex along the grain.  It had 3 sockets for tuning forks: one at 1/2 the length, one at 1/3, and one at 1/4.  We put a vibrating fork in the middle and flexed the board while Dave measured it with some sort of spectrum analyzer he had lying around. As we gradually increased the flex, a distinct "node" appeared where the 2nd partial jumped out of the spectrum--a little more flex and it disappeared.  This is the point where the salesman raises his eyebrows and the customer goes, "Oooooooo...."  A little more flex and another, weaker node appears for the 3rd partial. Move the fork to another socket and the same thing happens but at different degrees of flex. Using a different pitch fork does the same thing with different flex.  Dave and I spent the better part of a morning doing this with different pitch forks accumulating quite a pile of data. When we graphed it, Dave thought he saw the beginnings of a complex pattern, but all I saw was a bunch of dots.  As Del and Ron have already said, this data means very little because real soundboards are not crowned along the grain--at least not nearly enough to produce this sort of effect.<o:p></o:p><o:p> </o:p>So make a similar device that can be flexed across the grain the way soundboards are crowned, and what happens to the spectrum as you flex it?  Nothing.<o:p></o:p><o:p> </o:p>Draw your own conclusions.<o:p></o:p><o:p> </o:p>Bob Hohf<o:p></o:p>Wisconsin<o:p></o:p><o:p> </o:p><o:p> </o:p></div></body></html>