I've got an audio issue that seems to be a recurring subject, I have yet to find a solution to it however.

Everything worked just fine until a couple of hours into the game, about halfway through Hydroponics, when some of my audio stopped working. I still have sound effects and music, but audio logs, dialogue (or monologues in Shodans case) and menus don't make any sound at all anymore (which made the cut scene in Operations really weird).

I have tried running the game as administrator.
I have tried changing all the different audio settings the game has to offer.
I've tried installing an OpenAL (whatever that is) from a link I found in these forums

None of those made any difference and to me the weirdest thing is that it stopped working mid-game. Anyone got any ideas because it's kind of sad not to be able to hear Shodans lovely voice.

I run Windows Vista 32-bit.

That's really weird. Have you already tried a simple reboot of your computer?
Have you checked if it also happens in older savegames?

The computer has been rebooted several times since the issue appeared and I have also used several different save files. I've had the problem for maybe two weeks now, trying to solve it on my own, before I decided for this approach.

That's really strange, especially as some sounds still work. Have you updated or installed anything sound related?

Reinstall the DirectX 9 components to make sure everything is fine on that end.
http://www.microsoft.com/en-us/download/details.aspx?id=8109

Check for updated drivers for your soundcard.

And I'd also make backups of savegames, completely remove the game and all of its remains and make a fresh install.
Run this as Administrator (right-click the game's shortcut => Run as ..) and check if the problem persists. If not, copy back your saves and try again.

Turns out it was the level of the positional sound bias that did it. I just randomly fiddled around with the levels again to make sure I had really tried everything before a re-install and it suddenly works now! I think my speakers were interfering with it somehow, so it's probably an issue unique to me. Thanks a lot for your help!

;-) Yep, that's nothing we could have helped with much. Thanks for letting us know.

I believe this is a setting in the game itself. Hit the ESC key and select - Audio. Then select - Audio Options.
Click on box - Messages. If you have no sound / voices, it is probably set to "Messages Text". Click it until it reads
Messages Speech, or Messages Both.

Hope that helps!