
When Show Advanced Tools is selected in Advanced preferences, the Audio Bounce Extensions pane is available.
Audio Bounce Extensions preferences let you set the bounce extension and the surround format. The Bounce Extensions pane consists of the following preferences:

When Show Advanced Tools is selected in Advanced preferences, the following are available:
Stereo Left and Right fields: Sets the bounce extension for each audio file when bouncing in split format. You can change the extension by typing in the text field.
When Additional Surround Options is selected in Advanced preferences, the following are available:
Surround Show As pop-up menu: Sets the surround format. The choice you make automatically updates the remaining pop-up menus in the Bounce Extensions pane.
Surround Initialize button: Resets the bounce extensions to their default values.
Surround extensions fields: Determines the extensions that are appended to audio filenames when bouncing in surround format. You can change the extension by typing in the text field. The extensions also determine the channel assignment when importing split surround files.