The default install for Giants disables EAX, because when it came out it was considered a performance hit. In practice, it wasn't much of a hit then, let alone now, so you definately want it on.
Add -SND3D to your Giants shortcut to enable surround sound, and this also enables the Reverb and Occlusion options.
It could be argued that in this day and age, the GOG installer might want to enable that by default.

Wait...so the 1.4 + EAX patch isn't needed to provide EAX?
The strange thing is that, after installing that patch and replacing the .EXE with the one the GOG.com installer originally put there in order to get rid of a check for a CD that I don't have, I don't need to use that command line argument to enable reverb and occlusion. Also, the title splash screen has a big EAX logo in the middle along with the developer logos.

Right on! Works like a charm.

Thanks much for this, the game sounds great now!
EDIT - Hmmm, I may have spoken too soon. I just got three consecutive BSOD's in the same area (Mecc story 2 - High Village). When I removed that flag from the shortcut, no BSOD and I was able to complete the mission.

Well, fwiw, I'm quite a ways past that now with no problems. (Into ... 'act 4' I guess) This is with an X-Fi Elite Pro.

it didn't work for me. is it because i don't have a creative labs card? Im using the built in realtek card thats a part of my motherboard.

Yeah, I just had it happen again without the shortcut flag much later in the game. It only appears to happen when there are a large number of enemies on the screen, specifically a large group of Reavers. It's definitely a sound issue, the BSOD keeps referencing P17.sys (Creative sound driver) with one of those "DRIVER_IRQL_NOT_LESS_OR_EQUAL" errors. This is on an Audigy LS, which is really not the greatest sound card in the first place, but it still shouldn't be BSODing on this game (I've never had it do that before on any other app or game). I'm going to try a uninstall/reinstall and see what happens.

last time i saw that, it was because my sound card was dying. When i removed it and used the onboard one, it stopped BSODing.

Actually, I just confirmed there is nothing wrong with the sound card, its just the unstable EAX/3D sound support in Giants. First off, I didn't realize that I had used the shortcut that still had the -SND3D flag when this most recent BSOD occurred (I created two shortcuts for testing purposes), so that was likely the cause. Just to confirm, I installed a different sound card and tried it both with and without the -SND3D and it also BSODs at the same exact point when EAX/3D sound is enabled.

Well, that probably explains why the 3D sound was hidden in a command line option, apparently it wasn't finished yet.
That said, I've played all the way through Giants many times now without issue, over a number of years on several different computers. I'm trying to think of what might be the commonality to my success, but it's not obvious considering the large number of drivers I've had no problem under. Some thoughts:
- I'm always running in at least 5.1 surround sound
- I've always played Giants on real Creative cards. From the Awe64, SB Live!, Audigy and now X-FI. Other than that, sorry guys but I'm at a loss. I've never seen it -not- work.
Well, the only other thing I could suggest is good advice in general - all my sound cards get a dedicated IRQ; typically, that means PCI slot 3 (which may or may not be slot 3 on your board.) Later motherboards have a lot of on-board stuff that makes it challenging to isolate the card on it's own IRQ, and you have to read the manual carefully to discern what built-ins are on what IRQ's.
I can't say definitively that's the issue, only that I rarely/never have issues with sound and that's a build rule for everything I've designed and sold. If you're fighting with it to get that much superior sound, that might be something to look at.