While iMovie for iOS is a technological tour-de-force that somehow crams a complete video editor into the limited real estate of an iOS app, it does have its Achilles Heel -- a less-than-stellar ability to work with audio. Macworld author, TidBits Editor, and all-around nice guy Jeff Carlson, who also just happens to have written The iMovie '11 Project Book for Peachpit Press, has written a nice roundup of audio workarounds to help you with iMovie for iOS.
While I won't spoil the three well-written tips by repeating them here, I will give you an idea of Jeff's hints for getting the most out of audio in iMovie