I do a lot of sound engineering and have always been intrested in the reproduction or amplification of sound, live or recorded, as well as acoustics. I was thinking an interesting topic would be a presentation on Line Array theory, seeing as we have a section on music in the environment and I imagine we won't be able to go into to much depth on speakers.
If you go to any decent concert these days line array systems are used for the FOH, the theory behind it is quite nice (although I've never gone into any of the in-depth maths) and combines real world challenges and effects with an idealistic theory. It's basically a speaker system, normally hung from a ceiling, with speakers aligned in an array (column) to produce a much more efficient and even contrallable system (you can specifiy 'dead' zones for example where you don't want any sound). You could also look at subwoofers and patterns of the speakers (different microphones have different pickup patterns and speakers are basically reversed mics) and ways of amplifying and cancelling through speaker placement (e.g. to avoid subwoofers outputting a lot of bass onto a stage and only forwards). Or you could compare it to other style systems, such as point-source PAs (literally a speaker pointing at every point in the room, thats a big cluster of speakers!)
Its a big topic, but could be quite interesting! Here's a little intro article http://www.soundonsound.com/sos/mar06/articles/live_linearrays.htm