Recently purchased and installed Riven off of GOG.com, and I am unable to get Ambient Sounds to work. I have gone to the Options section of the in-game menu bar and have toggled Ambient Sounds on, but the environments are silent. There still is sound in the game--audio plays perfectly fine during movie sequences, and "important" sounds like manipulating levers are still audible--but "lesser" background effects like the waves crashing on the surf are mute. The Reference Sound buttons in the in-game Setup screens also don't play anything when clicked on.
Running Riven under Win XP Home Edition Service Pack 3. I have integrated sound instead of an actual sound card--a SigmaTel High Definition Audio CODEC, to be precise--but aside from not being able to initiate sound in the FEAR 2 demo, I've never had audio troubles.
Any help would be much appreciated.
EDIT: Upon further investigation, in-game background music also isn't playing. How strange!

If you find the ambient sounds in the game folder are you able to play them independantly of the game?

No. All the items in the Riven\data folder are .MHK files, and I haven't a clue how I would play the game's ambient sounds off of them.

I think those files are actually the movies and animations. Is there nothing in any of the other folders that looks like sound files?

Most of Riven's sounds are in .mp2 format, inside the .mhk files.
If you want to get to the sound files used in Riven you can use Riveal. It's a small java app, by Ron Hayter, and it's really easy to use to extract Riven's and other Myst series games resource files like audio, pictures and movies.
Riveal works perfectly on my XP Riven install. You can get Riveal latest vesion from here.

Not really. All that's in my Riven directory are:
bb_cvid.qtc
bb_dci.qtc
BB_MC32.qt
CMGR32.DLL
DHIO32.QTC
Extras.MHK
gfw_high.ico
goggame.dll
innosetup_license.txt
manual.pdf
Menus.dll
mohawk32.mmx
Mohawk.w32
QTIM32.DLL
Riven1.rvn (save file)
riven.cfg
Riven.exe
Riven.ini
riven.usr
SAVE.rvn
support.txt
unins000.dat
unins000.exe
unins000.ini
Then there's a "data" subfolder with all the MHK files in them (a_Data.MHK, a_Sounds.MHK, b2_data.MHK, etc. 20 files all total).
I'll try using Riveal, though I'm not sure if I'll know which sounds are the ambient sounds, and which are the regular sounds. Couldn't hurt to try, though.

I dunno will extracting them help?, I assume the developers put them in the .mhk files for a reason. The only other thing I can sugest is to try hardware sound acceleration and see if that does anything from the dxdiag menu.
You may also want to contact gog support if you haven't done so already with this problem.

Listened to all the WAV files Riveal spat out. They all seemed to work just fine. How strange.
Indeed, I'll pester GOG.com's support team about it, though I'll leave this topic open in case anyone happens to have some further suggestions.
Huh. I just realized that the background music also isn't working. This is a most peculiar issue.

I suggested extracting the audio files so that MatthewG could try your suggestion of trying to play the audio files independently from the game...

But if they are in a .mhk file wouldn't the game need to handle the sounds regardless what they are or would they still use the .wav file format inside the .mhk? I honestly don't know.

If i had to guess i'd say the game goes and gets whatever it needs at a certain point, an audio file, a pic or a movie, from within the .mhk, but the system where the game is installed still needs to have the ability to handle those files inside the .mhk, i.e., if a system couldn't handle .wav files at all because of missing codecs or for some reason, the game wouldn't be able to use them either.

Well, I can hear all the sound effects just fine after I extract them with Riveal, that's for sure. :)
So my computer can play audio okay. There's just something about Riven that's not fully agreeing with my computer.
If I can't get this stuff to work, is the game beatable without the ambient sounds/music being audible? Or do they come into play during puzzles at some point?

Actually, sounds do play a part in at least one of the puzzles, the one related to Riven's wildlife.
And the game is just not the same without sounds, you'd be missing out on alot.
Have you checked your in game top menu to make sure 'Ambient Sounds' is checked under the options tab ?

Yeah, that's why I haven't even been playing the game since I got it: I know how crucial the audio is to enjoying Myst games and immersing yourself in them. Practically half of the experience is cleaved away with the sound not working properly.
And toggling Ambient Sounds under Options was one of the first things I tried. I switched them off and then back on again multiple times, but it did nothing to remedy the problem.
By the way, I really appreciate all of you tossing around ideas. Thank you very much.

Did you allow the game to install the old version of quicktime?, I think the new version doesn't work with riven, not sure if thats what the game uses to play its music or not. You could try deleting quicktime if you have a new version of it and reinstall the game with the old version, maybe that will work?