TUNING digest 1541

Greetings,
Paul writes:
>Actually, thinking further on it, I don't think that would even be
>possible, considering that the beats don't actually exist physically,
>but arise because of nonlinearities in the auditory system.

Gee, I must beg to differ, based on two experiences.
I recently had a buzzing problem in a piano soundboard. It was
particularly loud in the middle bass region, and only audible at the attack
phase of the note. This short duration usually makes extraneous noises hard
to find.
When I detuned a unison in that area, I did so that it would beat about
three times a second, and immediately heard the buzz in the soundboard, (later
found to be small washer), vibrate in sympathy and emit its buzzes at the
same speed. I take this to demonstrate variable amplitude in the physical
sense.
The same thing happens in an airplane when the two engines of a twin get
out of synch. I have seen drinks and ashtrays throb with the difference
pulse. As a tuner it makes me want to go up front and start telling people in
uniform to do something about it............
Regards,
Ed Foote
Precision Piano Works
Nashville, Tn.

> Nevertheless, I remain skeptical about adding sine waves of matching
> frequency to eliminate beats. I haven't worked out all the math of it
> yet, but it just doesn't feel to me like it would work out.

It certainly doesn't make sens viewed in the frequency domain.

On Fri, 2 Oct 1998, Paul H. Erlich wrote:
> Paul H., the nonlinear processing that the ear does actually increases
> the frequency resolution over what the standard uncertainty relation
> would give for an analyzer with the ear's temporal resolution, thus
> decreasing (rather than creating) the incidence of beats.

?? I must be misunderstanding something. If you analyze the signal
using a process which decomposes it linearly, such as a Fourier
transform, no energy is detected at the beat frequency. What is a
decrease from nothing? I think this is what Gary Morrison was talking
about when he said (talking about bram's beat-canceling idea):

> It certainly doesn't make sens viewed in the frequency domain.

--pH http://library.wustl.edu/~manynote
O
/\ "Churchill? Can he run a hundred balls?"
-\-\-- o
NOTE: dehyphenate node to remove spamblock. <*>