How to automatically synchronize two recordings of the same event?
There is a plugin called vocalign that will do this. It is designed mainly for aligning vocal overdub and replacment dialog but it should work for what you are doing. You can use it as a VST in audacity. It isn't cheap but, if my memory serves me correct, it has a fully functioning demo.

http://www.synchroarts.com/index.php?PAGEID=products&amp;ID=vocalign