Renaming false beats...was False beats ....was M&A A

[ed440 at mindspring.com]

Dave-

I've seen how TuneLab shows two peaks for an out of tune unison pair. In that
situation there probably are two simultaneous and different frequencies generated
by two strings.

If TuneLab shows the same thing for a single false beating string, is this demonstrating
that the string is simultaneously producing two frequencies which generate an interference
pattern we hear as a beat?   Or is it possible that the display "holds on"
to the two peaks while the string alternates between two frequencies?

When we hear a beat between two close frequencies, we hear a periodic variation 
in amplitude, not a periodic variation in pitch.  

Sometimes in the mid-range we hear a string decay that rolls back and forth between
two higher partials.  I suppose this should be called a pertiodic change or timbre.
Is this somehow related to false beats in the higher treble?

Ed S.



-----Original Message-----
>From: "Porritt, David" <dporritt at mail.smu.edu>
>Sent: Feb 21, 2007 9:51 AM
>To: ed440 at mindspring.com, Pianotech List <pianotech at ptg.org>
>Subject: RE: Renaming false beats...was False beats ....was M&A A
>
>Ed:
>
>If you've ever seen or used TuneLab that has the spectrum display you
>can see the two different peaks representing two different frequencies
>coming from one string.  It's clear that there are two actual
>frequencies beating against each other.  To me there's no doubt that it
>is a pitch thing.
>
>dp
>
>David M. Porritt
>dporritt at smu.edu
>-----Original Message-----
>From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On
>Behalf Of ed440 at mindspring.com
>Sent: Wednesday, February 21, 2007 8:26 AM
>To: Pianotech List
>Subject: Renaming false beats...was False beats ....was M&A A
>
>For thinking purposes, how about "Apparent periodic pitch fluctuation?"
>
>Questions:
>
>Are we talking about one phenomenon of several phenomena with similar
>sounds?  If so, can we categorize the phenomena to avoid endless wheel
>spinning?  Can we provide a diagnostic for this?
>
>Is the phenomenon really a pitch change or a change of amplitude that we
>hear as a pitch change?
>
>Is the phenomenon a change of timbre that we hear as pitch change?
>
>Is the phenomenon mostly limited to the capo region, or does our
>perception assume the "beating quality" in this area?  Is this because
>of the mechanics of the capo (vs agraffe)?  Or is it because of the
>frequencies in the capo area; and if so, is this a matter of physics or
>psychophysics?
>
>Bass strings often exhibit warbles, beats and whines at high
>frequencies.  These problems originate in the string itself, not in the
>rest of the piano.  Does this bear any relation to sound anomalies in
>plainwire strings?
>
>Ed Sutton
>