Voicing and Inharmonicity

[DOUG RICHARDS]

     Bob and list,

     I have been one of the lurkers on the list for some time.  Your
     question about the frequency shift of the partials due to different
     hammer conditions sparked an idea.  From my experience in shock and
     vibration in the disk drive industry, I would suggest that the
     condition of the hammer should only change the amplitude of the
     partials, not the frequency.

     An example of this in my line of work would be Modal Analysis.  When
     trying to understand a vibrating mode shape of a structure, time
     domain data can be gathered to "animate" how the structure vibrates at
     a particular frequency.  If the frequency of interest is low, a soft
     tipped hammer is used to excite the structure.  When a high frequency
     resonance is being investigated, a harder tipped hammer is used.

     I would propose that the same principle would apply here.  Only the
     amplitude of the partials should change with no change to the
     inharmonicity.  Although a hammer is very nonlinear in compression, is
     only contacts the structure (string...) to excite it.  The response of
     the string is what generates the sound, and the hammer hardness will
     only dictate whether the higher partials have much energy content.
     Care would have to be taken in a real experiment to not change the
     coupling of the string to the soundboard or aggraffe since the
     structure would have changed.

     Just my thoughts...

     doug richards
     drichard@qntm.com
     Quantum Corp.
     Mechanical Engineer
     Lurking wanna be piano technician


     ______________________________ Reply Separator
     _________________________________ Subject: Voicing and Inharmonicity
     Author:  Robert Scott <rscott@wwnet.com> at SMTP Date:    3/9/97 11:45
     AM


     There seems to be myth that holds that inharmonicity is affected by
     voicing.  I would like to resolve this issue one way or the other.
     Can anyone report on an actual measurement of inharmonicity that they
     made that shows a difference in the number of cents of inharmoncity
     depending on how the string is struck?  My own experiments show
     no difference between striking the string with a felt hammer or using
     a light tap from a wooden paint stirring stick.  In both cases the
     pitch of the fundamental and all the partials remained the same.  Now
     I realize that the strength of the various partials depends a lot on
     how and where the string is struck.  But if a partial is measureable,
     it always shows up at exactly the same frequency, at least in my
     experience.  What do the rest of you say?

     -Bob Scott
     Ann Arbor, Michigan