
When Flex Pitch is turned on in the Audio Track Editor, you can adjust the gain of individual audio regions from –30 to +30 decibels.
Click the Show/Hide Flex button
in the Audio Track Editor menu bar.
Choose Flex Pitch from the Flex pop-up menu in the Audio Track Editor menu bar.
Select the regions you want to adjust in the Audio Track Editor.
Drag the Gain slider in the Audio Track Editor inspector horizontally to adjust the gain.

For more information about Flex editing, see Flex Time and Pitch overview