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This chapter is from the book

More Sound Advice

Waveform Tips

When you’ve used the View menu to display audio waveforms, iMovie HD’s timeline snapping feature snaps the playhead to silent portions of clips (specifically, when you scroll to within three frames of silence).

To work with more precision when viewing waveforms, zoom in on the timeline. If the audio in a track is on the quiet side, the waveform may be hard to see. Solution: select the audio clip and press the up-arrow key. This accentuates the spikes in the waveform. To make the spikes smaller, press the down-arrow key.

When you import an audio clip or music track, iMovie HD must render the track’s waveform—a red progress bar appears at the bottom of the audio track, and the waveform appears a bit blurry until iMovie HD renders it. Because this process takes some time, you may want to leave the waveform display turned off unless you need it for precise editing or volume adjustments.

Trimming Audio

You can trim the start and end of an audio clip using the same direct-trimming techniques described on page 232. As with video clips, you can reclaim audio that’s outside of a clip’s boundaries by resizing the clip.

Scrubbing Audio

Here’s a handy way to locate the exact spot to trim or split an audio clip. Zoom in on the timeline, then press the Option key while slowly dragging the iMovie HD playhead. Your audio plays back, but is slowed down. The sound even plays backwards when you drag the playhead to the left. (Beatles fans: import some White Album songs from your iTunes library and have fun.)

Extracting Audio

At times, you may want to use only the audio portion of a clip. For example, you’re making a documentary about your grandmother’s childhood and you’d like to show old photographs as she talks.

To do this, drag the video clip to the timeline, then select the clip and choose Extract Audio (1-J) from the Advanced menu. iMovie HD copies the audio, places it in Audio Track 1, and mutes the audio in the video clip.

Next, select the video clip in the timeline and press the Delete key. The video vanishes but its audio lingers on, and you can now position still images and other clips in the video’s place. You can also drag the audio elsewhere in the timeline.

Overlapping Audio in the Timeline

iMovie HD may provide just two audio tracks, but that doesn’t mean you’re limited to two simultaneous sounds. You can overlap multiple audio clips in the timeline’s audio tracks: simply drag one audio clip on top of another.

Repeating Sound Effects

You might want some sound effects to play for a long period of time. For example, iMovie HD’s Hard Rain sound effect is less than 10 seconds long, but maybe you need 30 seconds of rain sounds for a particular movie.

For cases like these, simply repeat the sound effect by dragging it from the Audio pane to the timeline as many times as needed. You can also duplicate a sound by Option-dragging it in the timeline. If the sound effect fades out (as Hard Rain does), overlap each copy to hide the fade.

You can build magnificently rich sound effect tracks by overlapping sounds. To create a thunderstorm, for example, drag the Thunder sound effect so that it overlaps Hard Rain. Add the Cold Wind sound while you’re at it. And don’t forget to use iMovie HD’s audio controls to fine-tune the relative levels of each effect.

Camcorder Sound Settings

Most miniDV camcorders provide two sound-recording settings: 12-bit and 16-bit. Always record using the 16-bit setting. If your sound and picture synchronization drift over the course of a long movie, it’s probably because you recorded using 12-bit audio.

Muting an Audio Track

You can mute an audio track entirely by unchecking the box to its right in the timeline viewer. If you uncheck the box next to the video track, iMovie HD mutes the video’s sound. This can be handy when you’re replacing the audio in a series of clips with an audio bed—a segment of background audio that will play across multiple clips.

Splitting Audio Clips

You can divide an audio clip into two or more separate clips whose position and volume you can adjust independently. First, select the audio clip you want to split. Next, position the playhead where you want to split the clip. Finally, choose Split Selected Audio Clip at Playhead from the Edit menu or press apple.gif-T.

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