I am an artist who is designing some interactive play equipment for a playground. One of the playground components is a talk tube feature. The child will speak into a flower sculpture, cone shaped flower attached to a stem made of hollow pipe, and underground tubing will carry the sound to another Flower approximately 15 20 feet away. I will be using 1-1/2" flexible smooth pvc pipe. My question is: will the zig zag design of the stems adversely affect the sound transmission? I am attaching a picture of the design so far[view showing angles of a talktube.
For the shapes you have drawn, the angles don't look much different from the old speaking tubes of ships and the grand houses where they were used to summon the maid. The length of the pipe is pretty short so I don't think you will have any problems, as long as the bends underground are not too sharp.
It's an imaginative idea, children's voices are high pitched and the early ship speaking tubes were designed with whistles in mind :)
I hope you get an answer with more detail but I can't think of an obvious problem.