I don't think so. Most cameras do not accept USB Mics. But I don't have the camera so I can't be sure.
I have a Zoom H4N.
The way I would think about it is this.
For best results, create .wav files with the Zoom. If you created MP3 files with the Zoom, convert them to AIFF in iTunes.
Drag your Video into a Project. Turn on the Audio Wave Forms so you can see that audio from the camera.
Now, drag in the WAV file or AIFF file and drop it on the Video Clip at the approximate place where it starts.
You should be able to see the Audio Wave Forms for the H4N clip as well. Set your Thumbnail Slider to 1/2 second so you can move the sound with some precision (to the frame level). (Also, to edit to the frame level, you can go to iMovie Preferences and select DISPLAY TIME AS HH:MM:SS:FRAMES.)
Now you can drag the audio track left or right to sync it up with the track from your camera. This is easiest if there is a loud noise such as a clap that you can see in both waveforms.
When it is lined up, you can mute the audio track from the camera so you just have your H4N audio.
A good trick to know is to add some black clips before and after your video track so you will have room to move the Zoom track left or right. You can trim away these black clips later if you don't need them.
Finally, if you need to edit this further, I suggest using SHARE/EXPORT USING QUICKTIME. Choose Movie to QuickTime Movie, and choose Apple Intermediate Codec for the Compression. Save this where you can find it and import it back into a new Event. Then you can edit the video and audio together as if you had made it on the camera.
If you do a lot of this, Final Cut Pro X will synchronize the Zoom to the Video clip automatically through the MultiCam feature. You can also edit the clip right away without having to export it and reimport it. Also, with FCPX, you can adjust the audio to 1/100 of a frame (rather than to the nearest frame) so the audio lines up perfectly. But if you are still using the iMac 20", I would stay away from Final Cut Pro X for performance reasons. Also, you would need Lion or Mountain Lion for FCPX.
First let me say that I am not a PluralEyes user.
I think that PluralEyes3 would work for this limited purpose. If all you want to do is to sync audio from the H4N to video clips from a single camera and continue to use iMovie, then PluralEyes will do it.
If you wanted to sync one or more audio sources and/or one or more video cameras, then PluralEyes would not do this unless you moved away from iMovie and went to a pro editor like Final Cut Pro, Avid Media Composer, or Adobe Premier. These editors have support for multicam clips. In iMovie, you would have to manually sync the various camera angles, much like I described above.
For an example of a multi-camera project, think of a music video where you have a camera shooting a wide angle of the band, a camera shooting the lead singer, a camera on the lead guitar, and a camera on the drummer. You might also have a master audio track, the audio tracks from each camera, and an audio track from isolation microphones on each instrument. In this project, you would want everything synced, and you would want the ability to make rapid cuts between the various cameras, and even to have the ability to temporarily boost the guitar audio as you are doing a closeup on the guitar player.
What you should know is that Final Cut Pro X has a very powerful syncing feature that will sync multiple audio, multiple cameras, etc. There is no need for Plural Eyes (although some legacy Final Cut Pro 7 users may be more comfortable with PluralEyes so they continue to use it.) The Final Cut Pro X version of multicam is more powerful than PluralEyes, although unless you are a pro using multiple camera angles, you may not notice, except for the smoother workflow.
So the choice to me would be
1) Do I spend $200 on Pluraleyes and get the ability to sync one camera with one audio source and continue to use iMovie?
2) Do I spend $300 on Final Cut Pro X and get multicam sync functionality built in, plus a great many more features as well. The caveat on Final Cut Pro X is that it is a pro tool. Even though it superficially looks a lot like iMovie and uses Projects and Events just like iMovie, there is still a significant learning curve. On the other hand, you can easily import iMovie Projects and Events into Final Cut Pro and continue to work on them there.
Just to muddy the water a little more, you can sometimes find deals on iTunes Gift Cards. Here is a Best Buy deal that offers a $100 iTunes Gift Card for $80. (Note: I think this is in the US only.) Buy three of these and you can get Final Cut Pro X for $240. (This deal may expire soon, but is still active as I post this. However, Best Buy and others run these promotions periodically.)
First I want to thank you for your retailed and extremely helpful answers. I am always astonished and grateful that people can be so responsive and their willingness to share their expertise.
My wife is a singing teacher and would like to make some instructional videos of her working with students of about 40 minutes in length. In our situation, the audio is more important than video. Our plan is to have her in a studio, probability at the piano and the student a few feet away. There will be an audience of other teachers who will, from time to time, be asking her questions as she works with the student.
My thought is to have just one camera with both her and the student in the frame. I am thinking now of my wife with a label mike, and the student with an another mike on a stand. Both mikes would be connected to the Zoom H4n and the onboard mikes of the H4N would be facing the audience to pick up comments and questions. Perhaps when a question is asked I might swing the camera to view the questioner.
As I am not a professional audio -video person, I would like to keep everything as simple as possible with one camera and use imovie 11. I don't think I want to learn another NLE program such as Final Cut Pro X with a steep learning curve. Originally I had thought to connect the H4N directly to the camera but the consensus seems to be to sync it in post. If this works out then we will make more of these videos. My original plan now discarded was to use a flip or possibly the Zoom Q3.