iMovie is a video editing software application that allows users to create and edit their own movies on their Mac computers. It comes with a variety of features, including the ability to record narration over pictures and video. If you find that your narration tool isn't working, there are a few possible causes, as well as a few possible troubleshooting solutions.
One possible reason that you're not hearing any audio from your narration during playback is because the volume leveler in your timeline has been muted. To resolve this issue, click the clock icon in the iMovie window to bring up the timeline view at the bottom of the window. In the timeline view, there are three check boxes, located beneath the sound icon. Make sure all three of these check boxes are checked. Two of these boxes are designated for audio playback, and if one is unchecked, this could be the reason your narration won't play back.
Set Mic Preferences
In order for iMovie to detect your voice over, the program needs to recognize the microphone that you're speaking into. You can test this by clicking the microphone icon in iMovie. This will open a small dialog box with a few configurable settings. Click the "Record from" bar to bring up your list of microphone inputs. If you're using the built-in microphone, select "Built-in microphone." Otherwise, select your USB microphone. Speak into the microphone while looking to see if the bars in the dialog box light up with green lights. If they do, this means that your microphone is detecting sound. If the bars aren't lighting up, slide your "Input volume" slider to the right while speaking into the microphone. Slide it far enough that the bars stay green. If they turn yellow or red, then the mic is picking up too much sound.
Third-party plugins help to enhance the iMovie experience, but are not designed by Apple. Sometimes these plugins make certain iMovie features incompatible. If you have added any third-party plugins to your iMovie app, remove them temporarily to see if they're the cause of the issue. Open your "Home" folder, followed by your "Library" folder, and then open "Quick Time." Click and drag the third-party plugins from this folder, and drop them on the desktop. Log out of iMovie, and then log back into it. If the issue has still not been resolved, you can place your third-party plugins back into the "Quick Time" folder.
Although the iMovie application may be responsible for improper communication between the microphone and itself, the computer may also be to blame. Setting your computer's system preferences to "built-in" will enable the computer to recognize the microphone inputs, and sends the proper communication to the iMovie app. Click the "Apple" logo on the desktop, and then select "System Preferences." Click "Sound" to open a dialog box. Set both the input and output settings to "built-in." Log out of iMovie, and then log back in.
Delete Preference File
On Mac computers, some applications have preferences files. These files have a range of purposes, but they can often hinder the performance of applications, and therefore, deleting them can sometimes solve problems that apps are having. Deleting the iMovie preference may very well remedy any problems you're having with the voice over process. To delete the iMovie preference, open your "Home" folder, followed by your "Library" folder, then open "Preferences." Look for the file named "com.apple.iMovieapp.plist." Move this file to the trash, but don't empty the trash yet. Log out of iMovie, and then log back in. If you can now record your voice over, then your problem is fixed, and you can empty the trash. Don't worry, iMovie will build a new preferences file on its own, replacing the defective one you deleted. If the problem was not solved, then place the iMovie preference back into the "Preferences" folder.