I thought I knew how to make custom sounds and I found a couple mini-tutorials that even say to do it the same way I am, but my sounds just won't play. For the sake of clarity, this is how I do it:

1) Create custom sound in Audacity, export as .WAV and place in the right folder in Data/Sound
2) "Edit" an existing sound file in the GECK, change the path to my WAV file.
3) Change ID, save as new form
4) Open my weapon > Art & Sound > Attack Sound set to the sound file I made.

Nowhere in there does it work. If I open the actual WAV file in a media player, it plays the sound, but the sound file in the GECK and of course in-game it just doesn't make any sound. WHY?! Not the first time this has happened.

Hmm...

I made some sounds and they worked. Here are some caveats to making custom sounds:

* The sample rate should be 22050 Hz mono (single channel) in Audacity or 22kHz if you check the wav file's properties in windows (right click on the file, choose properties then summary tab).
Scratch that, I just checked my files and I have made 22, 32 & 44Khz files and they all work.
* You need to put the files in a folder structure like this: \Data\Sound\Fx\SomeFolderYouMakeYourself
Note the 'Fx' sub-folder. I'll bet that is the issue.

That is correct... Music only needs to be inside the Music folder, but sounds must be inside the Sound\FX or Sound\Songs folder for them to work correctly.
Sample rates of custom WAVs or MP3s do not seem to be an issue.

Yeah, unfortunately that's not it. Mine are 44Khz - I'll try 22 for kicks but like we all said, probably not the problem.

I shortened it to "Data/Sound" but the file is actually in Data/Sound/sound/fx/weapon/toygun/fire/wpn_toygun_fire_2d.wav" so sadly that's not it...

And yes, it's supposed to be "Sound/sound/fx", somehow my BSA unpacker extracted the "sound" folder into another "sound" folder. I just put my sound with all the others.

[EDIT:] Yeah, no, the rate did crap all.

Dang, it won't play any sound I add. I copied the wpn_alienblaster_fire_2d into my new weapon folder and just renamed it wpn_toygun_fire_2d but when I select its file path it won't play the sound.

So this has nothing to do with my sound file. Something's funky here...

Alright, so I tried tricking it - I copied the alienblaster sound over and renamed it wpn_toygun_fire_2d, and renamed the actual sound wpn_toygun_fire_2d (rl). I set it to the fake (alienblaster) sound and restarted the GECK. When I clicked it and hit play, it worked - it played the alien blaster fire sound. I wanted to just delete that one and replace it with the actual toygun_fire sound, hoping it would just work in place without having to select it in the GECK.

After I got it working with the fake toygun_fire sound (alienblaster) I decided since it was playing sounds now to see first if it might play my sound, having restared the GECK, and this time it did worse:
http://i107.photobucket.com/albums/m315/Kaileo/GECK%20Error/GECKnosound.jpg

And better still, after I switched back to the fake toygun_fire sound, it gave me the same error message, despite 1) having worked not 5 seconds earlier and 2) actually being the alienblaster sound anyways... I restarted the GECK again, still set to the fake toygun_fire sound, and it still gives me that error message. WHY!?

One has to ask one's self, why would the BSA unpacker append an extra \sound folder? The Geck and the game are two different programs. On a hunch try putting your sound into \data\sound\fx\something and see if A ) you can link it in the Geck and B ) it will play in the game. As for the error, that sounds (no pun intended) like either the file is opened with another application or some kind of privilege issue with the OS.

I don't know what it is, but now it won't play any sounds in fx/weapon/toygun, the folder I made. Even if I add another sound to it (an existing one from another weapon) it always gives me that error message. And I have no other programs open.

I don't know how the file path should matter too terribly much, but I suppose I'll try it.

It does that when you select the Sound folder instead of the Data folder when extracting multiple files from the bsa, or from NOT selecting the sound folder when extracting a single file (the directory it goes to by default is different for a single file then for multiple files.. need to watch closely).
And yes.. the file path is not only important, it's critical. The path for sounds has to be Data\Sound\Fx\YourFolderName or Data\Sound\Songs\YourFolderName.. nothing else I've seen, including more nested folders, will make it happy. I just went through all this like 2 weeks ago when making my MP3 Player that uses both sounds files and music files.

Ah... I always extract to the data folder and always extract two or more files so I don't have to specify the exact destination folder.

Open it up again in Audacity, and just save. The GECK has severe issues with 0 second sounds.

...0 second sounds? Huh?

FINALLY! For a while it still gave me that error message so I started all over - I put it in Data/sound/fx/weapon/toygun/fire/wpn_toygun_fire_2d.wav , deleted the sound objects, restarted the GECK, made a new sound object, set the path and it WORKS.

So yes indeed, no matter where the unpacker put the rest of the files, sounds must be under Data/sound/fx no matter what. Thank you all.

So... one last question if I may -- when the main Fallout3.esm runs in the game, does it use the files I unpacked with FOMM or does it always run off the BSA files? By that I mean, could you delete a sound file to erase it from the game, or would it still take it from the BSA?

The way I see it, the game will look for the file first and then look in the BSA for it. So if you have a filename that matches a file in the BSA, the actual file will always be chosen over the BSA version. So, if you delete the file, the game will still use the version in the BSA.