I can tell you, if I create my own flight from the FSX main menu the sounds do NOT work.

They appear only if I load the "default" CS "Cleared for takeoff (KSEA)" flight. Then I can change to whichever location, and the sounds are still on.

I also tried to make a touch-and-go over my native URWA airport.
Cabin sounds like sliding window or captain announcements work fine but somehow I cannot hear the beeping of the avionics, for example the NDB radio signal.

Is there a special switch on the panel that turns the Morse signals on/off or... the sound issue is not completely solved yet? :-?