This article( http://www.technologyreview.com/articles... )talks about sound amplification without electricity.
Now this is the coolest thing I have heard in a while. Screw home inercoms or intercoms anywhere. Kind of reminds me of the movie Steamboy, where the captain comunicates with the rest of the castle by these pipes. I am not sure what these pipes where called. I think they used to be used before electricity was harnessed. I wonder if these are more effective than those pipes they used to use. They say this new way can amplifie the voice ten fold. However much that is.

*edit*
http://www.acoustics.org/press/132nd/2aa...
This website goes into more detail!