This video shows you how you can use the split function to create a gapped sound file in Audacity, where students have to fill in the missing word(s). By adding silence to the original recording, we make sure that they have some time for writing down the answer. Alternatively, you can crop a part of a recording and keep only that part you're interested in, by using the trim function.

By default, Audacity cannot create mp3 files from your recordings. It does allow you to export them to mp3, however, using a special codec - lame_enc.dll. This video will show you how to find this codec, how to install it, and how to use it in Audacity.