String noises revisited

[Ed Sutton]

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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