In Toolset, edit any one of the sound files (seagulls, wind gusts, whatever) and click on "Add Sounds". That'll give you a LOOOOONG list of sound files (note the handy 'play' tab at the top to test what they sound like. The Voices from the campaigns are all under "vs_xxxxx". Some are pretty obvious as they have "aribeth" or whatever in the title, others a little more obscure. Test freely. These sound files can be used to Create New Custom Sounds or can be Added to Conversations with the add sound function in the conversation editor. You can do pretty much anything with them.
Outside the Toolset, you can use NWExplorer to open up, say, "HotU Main Data" and then open "Sound". Again, all the campaign voice stuff has the "vs_" prefix. They can be exported from there as and how needed.