Instead of adding black to the voice annotation, I exported out of iPhoto the actual picture the sound annotation was associated with. I used the Export command, Jpeg format, at 640x480.
I then dragged the jpeg on to QuickTime Player to open the image in QT, selected all, and copied.
I then opened my .wav file in QuickTime, used the "Add Scaled" command, and QuickTime created a video track using the picture. Since I used Add Scaled, the photo is displayed for the entire duration of the audio track. I then exported as described earlier, then imported the new file into iPhoto.
I now have the actual photo displayed in iPhoto while the sound plays. Forget trying to match up sound annotations with the parent images. You can now link show/play both at the same time in iPhoto.
Try it. It's very cool.