impedance and empericism

[Richard Brekne]

The Five Lectures on Piano Acoustics deals with this in some detail. This
fine series of articles by some of the most prominent members of the Piano
tech community in the past 30 years will soon be available for your reading
pleasure online in a fully implemented http format. The work is being done
by some of our Sweedish freinds. It is quite a task so when its done I hope
you will all take the time to read through this (should be required
reading) and drop the sweeds a monumental thankyou note for preserving this
out of print document.

Delwin D Fandrich wrote:
> 
> ----- Original Message -----
> From: Conrad Hoffsommer <hoffsoco@martin.luther.edu>
> To: <pianotech@ptg.org>
> Sent: June 15, 2000 8:10 AM
> Subject: Re: impedance and empericism
> 
> > Jimrpt,
> >
> > At 09:52 06/15/2000 EDT, you wrote:
> >
> > > ,...... If a source of pitch/tone were such that it gave off a
> > >'measured'/'perceived' pitch of 440 hz at  70F , 10% RH and 22 mb AP
> would
> > >the 'perceived' pitch/tone be the same 440hz at 100F,  90% RH 26mb AP ?
> And
> > >the 'measured'?
> >
> >
> > Gut feeling:
> >
> > Yes.
> >
> > You have not changed the source, only the speed at which the vibrations
> > travel between source and receptor.  If the receptor were moving relative
> > to the source, I could see where there might be a difference in
> perception.
> > (Hello, Dr Doppler, etc.)
> 
> ---------------------------------------
> 
> Well, but we do change the source.
> 
> We tend to think of the bridge as a fixed termination point for the speaking
> portion of the string.  It is not.  It moves in response to the vibrations
> at the end of the string in a complex fashion.  That is, it moves, but it is
> not always in phase with the force at the end of the string.  Without doing
> a whole lot of thinking or analysis on this, I suspect that this could have
> the effect of making the string act as if it were either very slightly
> longer or shorter than it actually is depending on whether the bridge were
> moving in phase with the end of the string or 180º out of phase with the
> string.
> 
> Del

-- 
Richard Brekne
Associate PTG, N.P.T.F.
Bergen, Norway