I doubt any effect there. As long as the material is in its elastic state, which it had better be, the grain structure won't matter. The grain structure of metal affects primarily its strength, which is, by definition, at the upper boundary of the elastic range. It does not affect stiffness or density. We are accustomed to thinking of stiffness and strength being related, but when used in material science they are not.Donn wrote:...Not that I'm proposing that it's a valid consideration, but just for the sake of discussion, a bell may have a slightly heterogeneous composition with respect to crystalline microstructure etc., and you'd have to check with your experienced vibration engineers about that.
Personally, I think trombone and especially trumpet players are fooling themselves with discussions of material properties. But they are a nervous lot and they live and die by their perceptions, so I don't interfere.
The formation method is a different thing, though. It can leave residual stresses in the material that preload the material and affect the way it couples acoustically with the air vibrating inside it. I suspect the vibration of the brass is slightly important for trumpets and to a lesser extent for trombones. And it's perhaps important for French horns. But I challenge its importance for tubas, because of the types of sounds produced by tubas and because of the relevant frequency range. We just don't push up into those sibilant overtones, even with our version of edge. Any edge we produce that does get up into that range will probably get us a dirty look from the conductor.
And I am not prepared to dispute a significant effect resulting from slightly non-round bells. That, of course, affects the shape of the resonating chamber, which is important.
Rick "never come between a trumpet player and his preconceptions" Denney
