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Re: Old Topic with the scientists' unscientific reply - mainly forPer
Richard Sales wrote:
<snip>
> I do have an unscientific opinion. I do not believe the sound of metal
> instruments is because of aging but more because of the type of metal
> (brass) that was used and how it was formed.
<snip>
> I think this is an argument, like politics and religion, which one can
> not win. Maybe a real scientist can add some scientific data, but I will
> still take my old Super 20 or Mark VI over any of the pretty new axes
> that are on the market.
A real scientist? I've managed to fool NASA into thinking so for quite
awhile. :-)
When this subject came up a couple weeks ago, I talked to a metallurgist
friend about metal aging. He normally works on developing new alloys for
jet engine internals. Come to think of it, that's probably pretty
relevant, since jet engines and saxophones in operation are both full of
hot air and make loud, annoying noises.
It's been a long time since I looked at Art Benade's book on musical
acoustics, so any real acoustics jocks on the list should feel free to
offer corrections or howl in outrage. If memory serves, a textbook wind
instrument has infinitely stiff walls, and its sound is determined by
its shape, the mouthpiece, the player's oral cavity, the reed, etc. As
you move from a textbook idealization to a real-world instrument, the
walls are no longer infinitely stiff, and, if they become thin and
compliant enough, start to contribute to the sound by selectively
damping certain frequencies (the tone holes also provide damping, but
that's another issue). So, in principal, the properties of the metal can
affect the sound.
These properties can change over time, although thermodynamics dictates
that the changes usually happen slowly. During instrument construction,
metal is typically bent, rolled and generally abused, which work-hardens
it, building in internal stresses. The stresses can be annealed out by
heat treating, but if that isn't done, stress-relief can still occur
slowly over time via the motion of defects called dislocations,
resulting in a softer metal. Also, depending on the specific alloy and
its heat treatment history, additional phases may slowly precipitate
out, forming small islands within the bulk alloy. These islands may
coalesce over time, via a process called Ostwald ripening, to form fewer
but larger islands. There's also the issue of surface treatment--most
instruments are lacquered, but some are plated, and different platings
sound different. This suggests that if the surface were to oxidize over
time, it might affect the sound as well.
I don't know whether this stuff would be enough to cause an audible
difference over time; probably somebody at Selmer knows the answer. As
a physicist, my understanding of this is pretty superficial, and a real
metallurgist could probably offer a better explanation.
Having said all this, I haven't noticed changes in the sounds of my
seventies-vintage Mk VI soprano or tenor. Or, rather, any changes are
likely masked by changes in reeds and mouthpieces, and the fact that
aging seems to affect the player much worse than the instruments.
Brian