I just got this for free thanks to indiegala but I got Steam key. Upon installing and examining the files there I figured the game files are a copy-paste job from GoG installation (lol) and the game is, for some strange reason, configured to use mono sound!
So, my guide is relying on assumption that Steam and GoG versions are near identical in file structure and that GoG version hasn't been updated since Steam copy-paste and both are not using stereo. I'll post the guide on Steam as well but since this seems to be the origin, I am posting it here first.

Guide:
1. Backup "CONFIG.INI" (game's root folder) and "dosboxNORMAL.conf" (\DOSBOX subfolder)

2. In CONFIG replace these two lines:
SoundCard=0xe018
SoundDMA=5
(this makes the game use SB16, instead of SB8 with mono sound)

3. In dosboxNORMAL.conf replace whole [sblaster] section with following:
sbtype=sb16
sbbase=220
irq=7
dma=1
hdma=5
sbmixer=true
oplmode=auto
oplemu=default
oplrate=44100
(this makes the pre-configured dosbox actually emulate SB16, instead of SB8 with mono sound)

4. Save both files and run the game. Ideal place to test is right in the starting room where there is a pipe with leaking gas. Go near it, rotate your view and hear how the sound source changes point of origin.

5. If it doesn't work restore the backups.

That's all.

The difference is huge of course! GoG made such a double blunder with this by using mono setting to install the game with and then even using the same mono in dosbox (someone must have actually manually changed it to mono since by default dosbox comes configured for SB16) :)

Thanks for that, appears to work well. :)

You might appreciate this - https://www.gog.com/forum/general/voices_selector_for_the_game_normality