I'm building a public sound sculpture made of tuned aluminum pipes -- think wind chimes that people can play.

I want to include lower frequency chimes in the sculpture, but the fundamental frequency of these lower chimes gets overshadowed by the intensity of their overtones.

How can I reduce the intensity of the overtones (2nd-4th harmonics) for these lower chimes?

Specifically, I want to heighten the fundamental frequency of a chime at G3, 196 Hz. I'm using Schedule 40 Aluminum piping, with an Outer Diameter of 1.9 inches, and Inner diameter of 1.61 inches. I've calculated the length of pipe for this G3 frequency as 47 3/8 inches.

I've considered making incisions at the anti-nodes of the 2nd-4th harmonics, so as to lower their intensity. Alternatively I could also add material at these locations. Fundamentally, the question is where on the pipe should this alteration occur, such that its overtones are dampened to a great extent, while its fundamental remains strong.

Note that this mostly concerns the transverse modes of the pipe -- see this previous post

  • $\begingroup$ Pick a location where the amplitude of these overtones would be the largest and use a dampening system that is frequency selective, similar to the wolf tone eliminator for cellos: en.wikipedia.org/wiki/Wolf_tone. $\endgroup$ – CuriousOne Jul 7 '16 at 21:11
  • $\begingroup$ This is going to be mainly experimental, given you have both visual and acoustic aesthetics to thing about. Have you tried your incisions method? Presumably you don't like the visual effect of incisions and maybe a sharp nick produces acoustic reflexions you could experiment with pleasing shapen holes around the antinodes, something that you could replicate elsewhere as images rather than holes e.g. make the pipe represent an octopus's tentacle where only a few of the suckers are holes and are acoustically functional (ou probably don't want octopusses at all, that's just an example) ..... $\endgroup$ – WetSavannaAnimal Jul 8 '16 at 3:51

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