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If you're creating a 5.1 mix
1.make sure your channel strips output is set to *surround* and position the parts where you would like them to be.
2. go to File > Bounce...
3. Select either aiff or wav files
4. the sample rate should match your projects sample rate - though often 48khz is used for video - the video editor should know which is prefered.
5. Select the File Type as *Split*. This way you will get 6 different audio files when you bounce to represent the 5.1 surround format, e.g.:
6. Before bouncing make sure that Surround Bounce is ticked.