gzent

In the pure case, correct, any sleeve of limited thickness will not reject vibration as well as a very thick solid one. However, as in the case of accoustical insulation in speaker design, you can insulate the pipe so well that any remaining losses are inconsequential when compared to other losses in the path of the air column.

Its analagous to electrical transmission line theory: if you keep perfecting a low-loss transmission line then at some point the gain is outweighed by the cost.

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