We've never burned DVD-Audio so I'm not sure which settings you should use.
I'd start by using ISO9660 + UDF 1.02 filesystems (the same as DVD-Video) and disable support for Unicode in Advanced -> Restrictions -> UDF tab. Using the Standard Input mode, add your AUDIO_TS folder and click the big Write button. If it asks if it's the root folder answer No. If it asks anything else answer No as well. That should create a disc like the other DVD-Audio examples I've seen on the web.