Sounds do interesting things in round shapes, parabolas will bounce sound from a large area into one spot, or from that one spot to a large area and are used extensively in theaters. Another interesting phonomina is a Whisper Gallery where you can stand along one wall and sound bounces along the sphere, travelling straight and then bouncing off the wall until it hits the wall again, continuing around the inner surface of the circle.

Well, I just learned that there's one in Grand Central Station.

In the arched hallway outside the entrance, check out the engineering magic of the "whispering corners." When you and a companion stand in opposite corners and whisper, you can hear each other as well as if you were standing a foot apart.
 - http://www.newyorkmetro.com/pages/details/4218.htm

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