String noises revisited

[David Ilvedson]

Hi Allen,



Is this a Hamburg B?   Were you able to get the exact agraffe to match the original?



David Ilvedson, RPT

Pacifica, CA 94044







Original message

From: "Allen Wright" 

To: "Ed Sutton" , "Pianotech List" 

Received: 7/16/2008 12:49:54 PM

Subject: Re: String noises revisited





I replaced two agraffes on the most noticeable offenders today, and both notes were greatly improved; perhaps 60 - 70% less high whistle. The first one I replaced was on F#3, the note the customer was most annoyed by. That note was then so much quieter that the F next to it jumped out as being the worst, so I thought I'd better try it on that one as well. Obviously this could go on forever, and be quite time-consuming - so I've stopped it at that.





I do seem to notice some slight abrasions (in one of the holes especially) of the agraffes. The best guess I can make is that this noise, which is so common in that section of B's and D's, may be some kind of inherent scaling "characteristic" (tactful, no?) which is exacerbated by any imperfection in the corresponding agraffe. It's just not logical that this can only be related to agraffe problems; it wouldn't just be in that section. 





Like so many things dealing with piano tone, I haven't found a black-and-white solution. But at least it's greatly improved - so that all the notes in that section have the same amount of this noise - and the customer knows I've gone the whole nine yards. 





Allen Wright













On Jul 13, 2008, at 3:32 AM, Ed Sutton wrote:





Allen,

Not a lot of hope, short of redesigning the piano.

The longitudinal partial is being excited by the combined energies of the 7th and 8th partials.

If you can get the hammer to strike at exactly 1/7th or 1/8th of the string length, it may reduce the energy enough to stop the sound. This may be the reason for the old design rule to strike at 1/7th of the string length.

On smaller pianos the longitudinal mode may be at the 17th or 19th partials of plain wire strings.

Ed Sutton

----- Original Message -----

From: Allen Wright

To: Ed Sutton ; Pianotech List

Sent: Saturday, July 12, 2008 6:23 PM

Subject: Re: String noises revisited





Ed, 





This sounds like an exact description of what I'm dealing with. Octave three - 15th partial - disappears with pitch change; all yes.





I want to read Jim's book now....does he suggest any fix for this, or is it a scaling problem (or simply unavoidable) or what?





Allen









On Jul 12, 2008, at 2:38 AM, Ed Sutton wrote:





Allen-

  

If I understand Jim Ellis' book, in a 7 foot grand piano, longitudinal mode noises will tend to occur in octave 3, and they will tend almost always to be at or near the frequency of the 15th partial. There will probably be a slight delay after the attack and before the sound develops. If you make slight changes in the pitch of the string, the longitudinal mode sound will not change pitch, but will disappear when the pitch has changed such that the modes that excite the longitudinal mode are outside of its resonance band.
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