longitudinal mode vibrations

[Richard Moody]

Hi Jim,   
	Since no one asked, what are longitudinal mode vibrations?  How is it
detected?  Can it be measured?  Is there an audible quality to it other
than false beats?.  Is this a phenom. of bass strings? Is this caused by
the vibrations of the sound board, so that it would appear after the first
second? Maybe I have been glancing too fast over the discussions on this,
but once the sound board is set into motion doesn't that affect the way
the string vibrates? (which set the sb in motion to begin with?) Is this
what LMV is about? 

Ric V's
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> From: Jim Coleman, Sr. <pianotoo@imap2.asu.edu>
> Date: Wednesday, May 19, 1999 12:40 PM
> 
:
> 
> You will discover that the lower partials are not always the loudest.
> Especially in the Bass, sometimes the fundamental is almost missing.
> And, sometimes the 2nd partial is quite weak. Sometimes the 7th partial
> sticks out like a sore thumb. Then we have the matter of longitudinal
> mode vibrations which cause some very high peaks at sometimes the 25th
> partial or the 31st partial, or other odd partials. This is where a
> longitudinal partial is in conjunction with a transverse partial (the
> ones we normally relate to), you can hear a real fast beat between the
> two (mind you, this can be on a single string).
> 
> This should whet your appetite for awhile. BTW, no amount of voicing is
> going to get rid of that sharp peak if it is longitudinal in nature. In
> 1967 we did an experiment where we clamped vise grips on the bridge pin
> to eliminate the longitudinal peak, but of course that greatly modified
> the tone of the note.
> 
> Jim Coleman, Sr.
>