The Main Settings Audio Tab contains some advanced settings which should only be modified if you know what you are doing.  It is recommended that you stick with the Defaults for these settings.

However, this is where you would tell ContactTalk exactly what sound card device you have.  Sometimes, if you are having trouble hearing your speech engine speak through the speakers, a potential fix for the problem could be to identify your sound card under the Audio Out and Audio In Drop down lists.

The Advanced button contains even more advanced settings.  Again, you should only modify these if you know what you are doing.