Are you recording your audio separately from the video? If so, it's probably time that you learned about time code and how to sync audio-for-video with video.
If you're recording audio directly to the camera, and can't see a separate audio file, have you opened up the container file and created separate audio and video stream files?

I would expect that the audio and video are all crammed into one avi file. (AVI stands for Audio Video Interleaved.) It is possible to separate audio and video by demuxing, if you needed to mess with the audio in Audacity, for example.