etd accuracy

[Robert Scott]

Ron Nossaman asked:

 >>>>
I hear of ETD accuracy ranges in the
0.01 cent vicinity. Is this correct? Is it correct for the entire range of
the piano? I know the difficulties in getting a decent signal in the low
frequency ranges. I'm asking about processing capabilities given a decent
signal.
<<<<

Ron, I assume you are not asking about the internal accuracy of
ETDs, which is usually .01 cents or better.  Rather it seems you
are asking how precisely one can match a piano note to an ETD.

ETDs with a high-resolution display, such as Verituner, RCT, and TuneLab,
can match external pure tones to within .02 cents.  The trouble is
piano notes are not pure tones.  Strings with a moderate amount of
instability to them (false beats) may define a pitch to an accuracy
no better than .2 cents.  Then there is the sustain.  If the note
does not last long enough to see movement in the tuning display, then
small pitch variations cannot be seen.  This is the limiting factor
in accuracy for the high treble.

This is not a problem specifically with ETDs.  It is a problem inherent
in the tuning process itself, even in aural tuning.  The stability of
the note and the sustain are the limiting factors for accuracy.

As far as low frequencies go, I don't think that is very relevant, because
all ETDs use higher partials for the low notes, so they never try to
match low frequencies.

-Robert Scott
  Real-Time Specialties