Jim: Glad it was interesting. Good to know Jim, I find it’s rare that anyone can hear what I’m hearing, I realize these are very subtle distinctions, but I enjoy tuning into subtle details.
I agree that the vibration of the flute isn’t significantly acting as a “speaker” and sending out sound waves of it’s own. I think the resonance might affect the air column inside, however.
For instance, if it resonates too much, it turns too much of the sound energy into vibration, making it very loud and squawky, but not pleasant (say, a flute made of styrofoam, balsa, or paulownia). In a way like a banjo does, compared to a denser-top instrument like a guitar. On the other end, if it doesn’t resonate at all, because it’s dense and stiff, and only reflects the sound, then the air can’t vibrate as freely, and is sort of stifled. I think this happens with flutes that have overly thick walls.
In the middle would be resonating somewhat, which allows the air to move more freely, but reflecting somewhat, to project the sound outward. Getting the right balance across the whole tonal range isn’t possible, so every choice has compromises. The top flute makers seem to get more balance, so I think they fine tune the wall thickness, bore diameter, etc.
This is all assuming the material is stiff, like wood. Of course a mushy material like latex is going to dampen the sound and neither reflect nor vibrate, as much as wood does.
I do think the sound travels through the wood though. This has been studied in other wind instruments, where the soundwave actually extends out beyond the chamber, and returns back into it (bizzare, I know). This could mean the wood acts as a filter, coloring the sound as it moves through it. I’m not talking about sound that simply escapes through the wall of the flute, which would be minimal and almost imperceptible. It can be visualized as the peaks and troughs of the wave actually existing beyond the outer wall of the flute, rather than being contained within it. I don’t understand how this works, but physics is weirder the more I learn about it.
Conical Bore: I agree completely that the reflectivity is the dominant effect, this is proved out by making a flute of a much lighter wood, or pvc, which still sounds pretty good. And smoothness or roughness of bore has a huge impact on the sound. But it doesn’t mean the other aspects aren’t coloring the sound to some degree. I love the look of Cocus too, one of the best, it’s sad it’s so depleted. But there are lots of beautiful woods.
