In rec.radio.amateur.homebrew Henry Kolesnik wrote:
I'm not certain to which group I should post this question, so I'm shot
gunning hoping to find it. If anyone can point me, please do. However....
Has anyone used the HP 3582A audio spectrum analyzer to plot the freq
response of audio devices like mikes, speakers, etc. Knowing the mike
response I'd like to see the spectrum of plucked guitar strings and their
harmonics and see how different manufacturers sound varies in a plot. I got
a 3582A at a swap meet, its complex and probably overkill but that's what I
have and I am anxious to try it out and would appreciate any tips.
Thanks

I've done this, some years back, with much more primitive gear. and
found that the spectrum of a plucked guitar string varies with time;
ditto for the natural and left-hand-stopped harmonics. If you listen
closely, you can _hear_ the variation: the higher frequencies die much
more quickly.

I'm not sure of the physical mechanisms that are involved, but suspect
that they include the nonlinearities in the strings, the woods. The
shape of the soundbox probably has a strong influence as well, or so I
think. I would not be at all amazed to find that this holds true for
plucked chordophones in general.

I would expect the spectrum of a continuously-driven string -- a bowed
string, such as a violin, viola, violoncello, viol, or vielle string,
OTOH -- to have a spectrum that was closer to time-invariant, once
the string got up to constant amplitude and as long as the bowing
continued. A hurdy-gurdy wheel is the ideal here, since it acts as a
bow as long as it is being turned.

But you're wanting the response of a plucked string, not that of a
bowed string. I suppose you could try two different approaches. One of
them would be to build a rotating-wheel bowing machine to look at the
spectra of strings continuously-bowed with different speeds, at
various distances from the bridge, and at different pressures. Another
would be to build a mechanical string-plucker, so that you could get
consistent values of plucking force, while (again) varying force,
distance from the bridge, and so on.

An advantage of the mechanical plucking machine would be that you
would (should, in a perfect world) be able to use the output of
multiple runs where all the variables were the same, and that you
could build some very nice "3-d" plots to show the variation in
spectra as the distance from the bridge (or the force, or some other
variable) changed.

Still, it is an interesting project -- the more so to me since I've
been a classical guitarist for 49 years, and learned that strings from
different manufacturers, and even different styles of string from the
same manufacturer, can sound *very* different on the same instrument.
That was why Segovia standardized on Augustine strings -- or so he
told us one night, at a meeting of the Houston Classical Guitar
Society, back around 1965.

Unfortunately, the same strings can sound very different on two or
three different instruments, too. None of this is in any way easy.

This probably would get a fair amount of interest in, say,
rec.music.makers.

Posted to, and followups set to, rec.radio.amateur.homebrew, where
I read it.

--
Mike Andrews, W5EGO

Tired old sysadmin