It is very probable that homo sapiens has very early become aware
of how to use and change acoustical properies of their environments.
Archaeoacoustics is the science that tries to find out what can be said
about how this was done and what conclusions can be drawn from it.
There is not too much reliable information about it and the border
between speculation and serious sceptical research is somewhat blurred.
Nevertheless it is a relevant topic that might bring valuable results.
stone with echo inducing surface structure - http://www.mythicalireland.com/ancientsites/piperstown/piperstown.html
Steve Waller homepage: http://www.geocities.com/CapeCanaveral/9461