ETD question re: unisons

[Richard Moody]

----- Original Message -----
From: Michael Jorgensen <Michael.Jorgensen@cmich.edu>
To: <pianotech@ptg.org>
Sent: Thursday, February 15, 2001 4:05 AM
Subject: Re: ETD question re: unisons


>  Many individual strings can full blush for several
> seconds (be very close), only to suddenly register flat-- a whole cent flat
for
> a brief instant and suddenly return to full blush.  Could the soundboard be
> forcing/imposing a frequency against the will of the string and simply winning
> the battle for a second or less?
> -Mike Jorgensen
>
Of course the sound board is vibrating along with the string(s)  And the bridge
in between also.  But let us not forget that ETD's like all measuring machines
have limits.   At one point in our investigation we have to ask the question,
what are the limits, are we at the limit?.
    Another consideration that has not been addressed is that ETD's do not
actually measure the vibration rate of strings themselves.  They give us a read
out of what the microphone is picking up from sound vibrations excited by a
soundboard excited by piano strings.  AND some are converting to digital.  It
would be interesting to see if magnetic or ceramic pickups gave the same or
different readings.
    This  gets to the determiniation of the accuracy of the instrument.  If two
instruments (of different design) always give the same reading it is reasonable
to assume the readings are "true".  This begs the question, "how do the 3 ETD's
(RCT, SAT, and TL (TuneLab) read a unison then a single string of that
ison?   ---ric