You can adjust the rate at which the volume of video or audio clips fades in and out.
Using the Audio inspector:
In the Project browser, double-click a video clip, the green or purple bar that represents an audio clip, or the green or purple background music well, and then click Audio at the top of the inspector that opens.
To set the rate at which the audio fades in, select Fade In: Manual, and then drag the slider to the left to make the audio fade in faster, or to the right to make it fade in more slowly.
To set the rate at which the audio fades out, select Fade Out: Manual, and then drag the slider to the left to make the audio fade out faster, or to the right to make it fade out more slowly.
Using fade handles:
With your project open, click the Audio Waveform button at the bottom of the Project browser.
Waveforms for each of the sound elements in your project appear in green, purple, or blue bands below the video clips. Blue waveforms represent the sound recorded with your video clips; green and purple waveforms represent sounds and music you’ve added to your project. Names appear in the top-left corner of waveforms to make it easy to identify them.
When you move your pointer over a waveform, small gray fade handles appear at each end, above the volume bar.
To adjust the rate at which audio fades in, drag the clip’s left fade handle; the waveform adjusts accordingly.
To adjust the rate at which audio fades out, drag the clip’s right fade handle; the waveform adjusts accordingly.
To play back your changes, move the playhead (the vertical red line) to the left of the clip you changed, and then press the Space bar.
Press the Space bar again to stop playback.
Click the Audio Waveform button again to hide the waveforms.