I posed a question about the validity of cryogenic treatment of brass instruments to the sci.chem, sci.physics, and alt.sci.physics.acoustics usenet newsgroups. The discussions wandered a bit off-track into cryo treatment of cymbols, knives, gun barrels, and steel in general. Some respondents mis-interpreted the processes as one of temperature shock treatment. However, some of the responses were to the point. I have extracted some of (what I consider to be) the more credible comments here. If you wish to see the whole discussion, you can search the appropriate newsgroups on deja.com.
subject: cryogenic treatment of metals
I'm not a working metallurgist, but I'm going to go out on a limb here: This idea is nonsense. Not much happens in metals at room temperature, and even less happens at metals below room temperature. You don't anneal materials by chilling them, but by heating them. You will indeed cause some cycling stresses by lowering then raising the temperature, and I suppose this might incidently work some beneficial change, but this is grasping at straws. The idea is nonsense.
However, brass *does* have a nontrivial structure, and if I recall correctly, can have ordered sublattices. And, of course, *all* metals have defects, and also grains and grain-boundaries, as others have pointed out. These can be manipulated by temperature and stress, so it's not a completely absurd idea, just a bit unlikely. And, as I say, probably wholly unrelated to steel even if it does work.
Peter G. Hamer:
While I find the discussion on cymbals interesting, I find the suggestion on wind instruments very difficult to credit.
Changes to crystal structure (eg due to defect movement) could change the vibration of a cymbal. OTOH surely the major feature of `brass' instruments is the major mismatch in characteristics between the air in the instrument and the metal of which it is constructed. A small change in the metals properties couldn't effect this mismatch very much.
subject: cryogenic treatment of brass instruments
In my brass instrument modeling, I found the major influences were the mouthpiece, tube shape/bell flare and of course the player's proficiency :-)
A rather long post from Joseph S. Wisniewski
Here's what we "really" do know.
1) The walls of a flute do not participate measurably or noticeably in the sound production. Benade aside, still living acousticians such as Coltman have done much to validate or dispel statements about gold or silver or platinum or various alloys of these metals. Coltman did some fascinating double blind tests of different metals against each other, and against some oddball materials (including cardboard and concrete). No contribution to the sound making process.
2) People who have done work on other woodwinds (including sax, which has the highest ratio of enclosed airspace to metal mass of any woodwind) and brasswinds like trumpet and English horn (Fletcher, Nedervee, Coltman, Rossing, sorry about the spellings) have gotten similar results. Including some published papers utilizing nearfield acoustical holography and vibration sensors mounted on the walls of the horn.
3) The measurable change in physical properties (hardness and modulus of elasticity) produced in cryogenic treatment is much smaller than the tolerance variations introduced by variations in wall thickness produced by tubing manufacturers from batch to batch, variations in hardness and elasticity produced by tolerance drift in the metal drawing and forming processes, contamination of the alloys, and variations in machining and soldering processes.
4) Everything that the Miyazawa web site [http://www.miyazawa.com/tech3.htm] that you pointed us to, as far as metallurgical effects that can actually be measured, indicates that cryo treatment has exactly the same effect on the metal as heat hardening (increased strength, hardness, and stiffness of silver, no noticible effect on gold). Although 50 hours of cryo treatment looks like it would cost about 100 to 1000 times as much as a four hour heat hardening.
5) Cryo treatment (and heat hardening for that matter) can't be done with the pads in place. Any time a competent instrument technician dismantles and reassembles a flute, you either replace or at least readjust and reshim the pads, as well as adjusting (regulating) the mechanism. The end result is exactly the benefit that is quoted for the Cryo treatment "Virtually all the instruments treated have an increased capacity to play softer and louder, by as much as 30%. (This is based on substantial anecdotal evidence, not a decibel meter.)" Plus other stuff about increased pitch stability, cleaner attacks, and evenness of tone, all widely acknowledged benefits of repadding and readjustment.
What's more, we have measured, on a good sound meter, the effects of a competent repadding on a flute, and it's way more than 30% louder or softer. This even includes most brand new, freshly padded flutes.
So, unless they can show us some measurable results, with a really masterfully padded and regulated flute as a starting point, I'd put the claims of the Cryo folks over in the shallow end of the credibility pool.
The New York Times published a relevent and timely article on November 2, 1999: "For the Musical Alchemist, a New Tack: Cryogenics." This article by TERRY H. SCHWADRON hits both sides of the debate. The article is available electronically (registration required - but it's free).
The conclusion? The question of whether or not cyrogenic treatment of (brass) instruments is beneficial in any way is still open for debate. Little or no scientific research has been conducted to prove or disprove the claims.