Is there any audio processing steps to remove, from a recording, that
> "boxy" (multi-echo) sound that results from using a single microphone
> in a large room?
Was there a single sound source such as one person talking and standing still? If you have multiple sound sources, the problem is a lot harder.
If you own a couple of CM-5s (Connection Machine), the code to do the process won't take very long to run. If you want run it on a PC it will take a little longer. The first step is to FFT to whole thing. If it is very long, and is high quality audio, it will take a while.