The use of alternate sound folders has been completely changed. You now have to manually specify which sound folder is to be used with a given series mod.
The down-side of this change is that selection of the soundd folder is no longer automatic (there''s a new page in the Settings dialog that allows you to add, edit, and delete series mod/sound folder associations).

The up-sides are that you can name your sound folder anything you want (but it still has to reside in the sim folder, and the sound folder name CANNOT contain space characters), multiple series mods can use the same sound folder (TPTCC and PTA for instance), and the amount of hard drive space dedicated to sound folders can potentially be dramatically reduced