Change the gain of audio regions in Logic Pro for Mac
You can change the gain of audio regions with the Gain tool, or in the region or cell inspector.
Gain changes have a 60 dB range — from -30 dB to +30 dB.
Change the gain of regions in the Tracks area with the Gain tool
Select one or more regions, or use the Marquee tool to select an area to be edited, which can included portions of multiple regions.
Select the Gain tool
from the Tool menu in the Tracks area. 
Drag the pointer vertically over the region to increase or decrease the gain. The numerical gain value updates as you drag. If you selected a portion of a region with the Marquee tool, then used the gain tool to adjust the gain of the the selected portion, a new region is created with the gain change applied to it.
Change the gain in the region inspector
Select one or more regions in the Tracks area or cells in the Live Loops grid.
Click the Inspector button in the toolbar.
Click the region or cell inspector to show region or cell parameters.
Double-click Gain, then enter a numerical value in dB:
To raise the gain, enter just the number.
To lower the gain, enter the Minus (-) key, then enter a number.
