[Angel]

Mark asked:

"I am interested if there is a maximum thickness before it effects the bansuri sound."

Tube walls in a flute have some influence in a way that is different as the common sense dictates.
First of all, remember that a flute -and any wind- is a aerophone, where sound is governed by the vibrations of the air column and not by the material of what the tube is made.
Material doesn't "resonate" in a traditional way, and has non direct but secondary influence in sound.
Wall thickness afects several things:

*toneholes height: this is a kind of resistance opposite to air molecules movement. Each tonehole is an air body by itself that has an inerce, that the main vibrant air column must move. The height of the tonehole
-say, the wall thickness- increases this air body volume and thus the resistance, making the air molecules to move more distance at the same time required by the frequency. The result is that, other things equal, the thicker the lower the frequency.
here, almost the same acoustical effect is obtained by bevel and undercut the toneholes.

*embouchure height: there are some interesting things here, related to aerodinamics of the air jet, that are very subtle. The real thing is that a thin wall at the embouchure gives (other things equal) more harmonics than a thick wall.This is a thing that contributes to the belief that the material is "resonating" because the flute has a more brillant sound...but look at the embouchure and not at the rest of the tube!
Anyway, is an oversimplification, since there are several facts acting here.
A thin walled embouchure has also a similar effect in frequency as described for toneholes.

I'm sure that thin walls of bansuri contributes to its sound, but one must see more at the regularity of inner walls and geometry of the bamboo used to make them.


About that, here are made some low bansuri with Bolivian bamboos originally used to make "toyos". The toyo is a low pitched panflute, sometimes made with joined sections of bamboo, and sometimes with a single one. This is a really long internode thing, man. I saw in La Paz a single pieced toyo with the longest tube of 1,60meters and about 3 cm diameter, perfectly cylindrical and no nodes except the far end.And very very thin walls
Also some traditional moseños are made in really long internoded bamboo. I think that are Rhypidocladum harmonicum and Aulonemia queko respectivelly. Yes, I know that are hard to find...(I didn't buy this toyo because I had much travell ahead)

Allow me here to remember some Richard Waters' comment at the old bamboonet. He is an instrument maker and bamboo lover who lives in Hawaii. He reffered to Schizostachyum species as long internoded and thin walled useful for flutes -more specivically the yellow and green striped one, the S. glaucifolium. At the Am Bamb Soc Sourcelist I read that S. sp "Murray Island" is used in Solomon islands to make panflutes (the same as Bolivian bamboos)
Never tried them personally but just an idea.

If I have to make a bansuri and imitate the thin walls and perfect geometry, I would look for a young culm, inmature, Ph aurea or better, Ph. nigra, using the middle part (between the base and the branches) where Ph are the most cylindrical.
...Sometimes...sometimes...a young Ph aurea that no colapse -means that dries without cracking or implode- has weak septums and perfect inner walls surface. Anyway, the elimination of the septums must be perfect.

I make a kind of quenas with these bamboo when I got them - very thin walled but strong enough to have an excellent sound. I normally laquer them inside.

Phyllostachys nigra uses to have the same characteristics described above.

Well, just some ideas

Angel