PowerPoint users always want to add audio to their presentations—either as voiceover sounds or background music tracks. However, since PowerPoint offers no native sound fades, most of these tracks need to be faded using a sound editing application.
For this tutorial, we are using Sound Forge on Windows XP Professional, but the same techniques should work with earlier versions of Sound Forge. In most cases, other sound editors work in the same way.
- Launch Sound Forge and open your digital sound or music file (WAV, MP3, CDA, WMA, ASF, etc.). Play your file to get an idea of how it sounds.
Figure 1: The Sound Forge interface is easy to understand
- In Figure 1, you can see how a sound file is displayed. Since we have opened a stereo file, you see two sound waves (data) shown representing the left and right stereo channels. Each channel can be edited independent of each other, as well as together.
- Your file will be represented as sound waves (two of them if you open a stereo sound file), as you can see in Figure 1, above. The sound waves taper into oblivion towards the right. This means the sound already has a fade-out (de-crescendo) processed. Select the entire sound file by pressing Ctrl+A or select part of the beginning by dragging over part of the area (see Figure 2).
Figure 2: The sound waves' color change to show that the displayed sound is selected
- Now choose the Process | Fade | In option. Sound Forge will create a fade-in (crescendo) effect, as can be seen in Figure 3. Play again to ensure that you are satisfied with the effect. Otherwise, undo (Ctrl+Z) and try again after choosing more or less of the beginning area.
Figure 3: Fade in effect
- You'll notice a distinctive fade-in within the sound wave display. Compare what you see in Figure 3 with the waves in Figure 2, when the fade-ins were not applied.
- Save your sound file to a file format. Sound Forge allows you to save as MP3, WAV and WMA, and PowerPoint can accept these formats through its Insert options. However, if you need to add a transition sound in PowerPoint, you can only use the WAV format.
- Use the same techniques to add fade-out effects. Substitute the actual process command to Process | Fade | Out. Save again to your chosen format.
Sound Forge allows much more control over fades if you use the Process | Fade | Graphic... option.
In addition to the Fade option, Sound Forge's Process menu contains several effects you might want to experiment with (see Figure 4).
Figure 4: The Process menu allows to you do much more than fades