iMovie and Final Cut are pretty forgiving for importing and exporting audio, but not always.
If your exported iMovie doesn’t play the audio portion, try converting the mp3 to AIFF format using iTunes, then import the AIFF version of the audio into iMovie.
– Open PC version of iTunes.
– Add your mp3 audi file to iTunes library.
– Choose iTunes > Preferences
– Click the Importing icon at the top.
– In the Importing dialog, choose AIFF Encoder from the Import Using pop-up, then choose Custom from the Setting pop-up menu.
– In the AIFF Encoder dialog, choose these settings:
Sample rate: 48,000 kHz
Sample bit: 16 bit
– In the importing dialog, click OK.
– In the iTunes library, select the mp3 you just uploaded to the library.
– Choose Advanced > Convert selection to AIFF.
iTunes places the AIFF next to the mp3. Import the AIFF into iMovie.