How the New Noise Filter Works
iMovie '11 allows you to set the volume for specific portions of your presentation, making it much easier and more versatile to use than earlier versions of the software. iMovie shows audio waves when editing sounds. These waves are color coded so you can visually observe sound that is booming or sound that is whisper quiet. To adjust iMovie audio levels of a clip, simply drag the volume slider located on the editing panel. The audio waves adjust as soon as you make changes. This allows you to see what you'll hear. iMovie's new Single Row View displays your entire movie project in one horizontal row. This makes it easier to preview as well as edit your soundtrack. The noise filter drowns out sound through the equalizer. You can also layer audio tracks.
To use the noise filter, open iMovie and display your iMovie clip or clips in the iMovie Project Library. Click on "Single Row View" button. The button is located on the upper right corner of the project library. It's one of a single row of three buttons.
Now turn on your "Audio Waveform Viewer" by clicking the grey button in the middle of the screen. Your audio wave will display at the bottom of your clip. Grab the "Volume Line" and drag the waves up or down to control the sound. While this is available on earlier versions of iMovie such as iMovie '09, what's different is that the iMovie '11 Noise Filter allows you to select just a section of the audio and adjust the volume for that section alone. You can erase the sound in that section, or turn the audio up or down. If you make a volume adjustment you don't want, simply detach the audio using the main iMovie menu. On the main menu at the top of the screen, select "Clip," then select "Detach Audio."
If you have a video with an unwanted background buzz or humm, the iMovie Noise Filter lets you drown out the section of volume while still allowing you to display the video. You can also use the iMovie inspector to add special effect audio to the clip or clips. This adds a dimension of control that videographers who love editing with iMovie had been asking Apple to add, making users rate the noise filter application a definite improvement.