Yup, you sure can. Just open up the Window, and underneath the playhead you'll see two little hash marks. Adjust those to encompass the audio you want, then go to Edit>Extract Tracks>Sound Track. A new little window saying Untitled.mov or Untitled.mpeg or what have you will pop up. The go to File>Export and export it as either .WAV or AIFF. Then open it in iTunes, and Convert Selection to MP3. I'm sure there's an easier way, but that's all I could figure out.