You can reuse or copy audio or narration from one project to another. Here's how:
- Open the first project that contains the audio that you need
- Export the audio.
- Close the project.
- Open the other project.
- Import the audio.
Since audio is stored in the PPTA file, you must export the audio from the first presentation and then import it into the other. Also, note that copying a slide from one presentation to another will not copy the audio associated with it.