There are 4 ways you can adjust audio on your timeline in Studio under Edit:
In Edit Mode, click on the "Toolbox" menu and "Change Volume." The Change Volume Toolbox will open. You can also open these settings by clicking the AudioToolbox button at the upper left hand corner of the Timeline and selecting the Change Volume (speaker) tab The Toolbox displays a audio mixer with controls for each of the three audio tracks on the timeline (Original audio, Sound Effects and Music):
1. Global volume control: This is a knob icon at the top of each track's volume meter. You can raise or lower the volume on the entire audio track by turning the volume much as you would audio on your stereo.
2. Specific volume control: The slider changes the volume at the current position of the scrubber within the movie.
3. Mute button: This is a speaker icon located to the left of your Global volume control. It will mute the audio in the entire track.
4. Fade In and Fade Out buttons: These triangular buttons below the volume slider make the audio fade in or fade out starting at current position of the scrubber within the movie
You can also adjust the volume directly on the Timeline by selecting the clip, and then clicking and dragging on the volume line in the center of the clip. Raising the line increases the volume, lowering the line decreases the volume.