Hmm. Actually I was not even aware of that static property. In that post I was talking about AudioSource.volume.
I believe AudioListener.volume is the global sound, so if it didn't affect NGUI sounds before then it was bugged and likely fixed in a recent update to Unity itself.
Yes, I dove into the NGUI code while debugging and compared Unity 4.2 to 4.3 and can confirm that AudioListener.volume == 0 does not affect added audio source volume (added by NGUI) in 4.2 but it indeed does in 4.3...
Since it does affect already playing sounds I guess they had missed to apply the master volume to sounds dynamically added later (seems a bit strange, but who knows).
Hehe, funny, I actually used that Unity bug thinking it was some kind of "automagical" feature of NGUI to separate the GUI from the game.
"It's not a bug it's a feature" FTW
Thank you for your quick responses and for a great product!
/ufot