iMovie is perfectly capable of stripping the audio portion of your footage apart from the video. All you have to do is click the video clip in question and then choose Advanced → Extract Audio.
As shown in Figure 8-15, the recorded audio suddenly shows up in your first audio track as an independent audio clip; its pushpins indicate that it’s been locked to the original video.
This command unleashes all kinds of useful new tricks that are impossible to achieve any other way:
Make an echo. This is a cool one. Copy the extracted clip and paste it right back into the audio track—and then position it a few frames to the right of the original, as shown at bottom in Figure 8-15. Use the slider at the bottom of the Timeline Viewer to make it slightly quieter than the original. Repeat a couple more times, until you’ve got a realistic echo or reverb sound. (iMovie 6 has its own Delay and Reverb controls, as described earlier in this chapter. But using this technique, you can control the length and position of each individual echo.)
Boost the audio. The Volume slider at the bottom of the Timeline Viewer is a terrific help in boosting feeble camcorder audio. It does, however, have its limit: it can’t crank the volume more than 50 percent above the original level.
Sometimes, even that’s not enough to rescue a line of mumbled dialog, or the distant utterances of eighth-graders on the school stage 100 yards away.
When all else fails, try this crazy technique: Copy ...