difference tones

[Richard Moody]

Jim,
    It is so great to see you back.  I had some questions I wanted to ask
about the speed of sound through air.  I know it is affected by temperature,
but what about humidity, or should I say 'relative humidity'? I am wondering
if this plays a role in difference tones?
    The "difference tone"  is very audible (in certain ranges) when tuning a
pure fifth that many of the historical temperaments require.  There a
difference tone in thirds also.  If listening to a synthesizer in very good
ET you can hear them in fifths and thirds
also.
On occasion I hear them when tuning pianos (in ET)  but not all the time.  I
always wondered why sometimes I heard these low tones when most of the time
I did not. ---ric


----- Original Message -----
From: Jim Coleman, Sr. <pianotoo@imap2.asu.edu>
.> I played violin
> until 7 weeks ago. It is common to hear the difference tone between two
> strings when tuning a 5th. The difference tone is an octave below the
lower
> string of the 5th. There are also summation tones which are a 10th above
> the lower note of a 5th. Obviously when you add the frequencies of A-440
> and E-660, you get C#-1100 (we're talking pure intervals here, not
> tempered). When you subtract 440 from 660, you get 220



> If I remember correctly, Wm. Braid White mentions this phenomena as well
as
> the Ellis translation of Helmholtz.
>
> Now to the other subject of single strings exhibiting a difference of
pitch
> from three strings which are tuned identically. In my studies, I found
> that this difference exhibits itself more in the 5th and early 6th
> octave on the piano and not as much elsewhere. I have not found 1 and 2
> cent variances as some have claimed. What are your findings? I find
> greater differences between the pitches of the prompt sound and the
> later decay sound (the TuneLab shows this quite clearly). It is easy to
> confuse these two sources.
>
> Jim Coleman, Sr.