Can't understand why, but chatter works again.
The only part of logfile regarding audio that I'm able to find is following:
Initializing DirectSound playback device...
Primary buffer created.
Playback format is set : sampling rate = 22050, num channels = 2.
Not enought hardware buffers (0), hardware disabled
Buffer caps : Transfer rate = 0, CPU overhead = 0.
Default speaker config is : 1310724.
Direct sound audio device initialized successfully :
DX Version : 7
Hardware - disabled [buffers : 0]
Extensions - enabled :
EAX ver. 1 [ ] - disabled
EAX ver. 2 [ ] - disabled
EAX ver. 3 [ ] - disabled
I3D ver. 2 [ ] - disabled
ZoomFX [ ] - disabled
MacroFX [ ] - disabled
SIMD render [X]
num channels 32
Cannot open audio file samples/infinite 1
I tried running two different campaign missions and only in second one I couldn't hear a few chatter at its beginning, then worked regularly. Also, I tested in FMB, building a simple two-ships flight on Burma_RRR map, having no missing chat.
Shocked and embarassed: never had such troubles with a Cyberolas' map...