Having been around here for a few months I noticed that unlike graphics, network, ai, etc.. audio doesn't have an own forum section.

Makes me wonder:

1. Why isn't there one?

2. Where to post audio related question?

You may have overlooked it.

Check out the Music and Sound forum that covers audio itself.

If you want to discuss the software systems about audio, several of the programming forums (Game Programming, APIs and Tools, or even Mobile and Consoles) may be appropriate depending on your specific questions.