I posted this on a GameSpot Forum thread in response to a complaint about the game's voice acting:

Here is how I was able to change the TEC frigate factory selection sound (which sounds like somebody sucking water through a straw):

 1) create a subdirectory called Sounds.Backups in the  C:\Program Files (x86)\Stardock Games\Sins of a Solar Empire\Sound directory (or whereever it is you installed the game at).  Copy all the Sound directory into the Sounds.Backups directory so it's easy to revert back if something goes wrong.

2) Find this file:

C:\Program Files (x86)\Stardock Games\Sins of a Solar Empire\Sound\PlanetModule_TechOrbitalFrigateFactory_OnSelection_0.ogg

rename it to:

PlanetModule_TechOrbitalFrigateFactory_OnSelection_0 WAS ORIGINAL.ogg

3) Copy/Paste this file:

C:\Program Files (x86)\Stardock Games\Sins of a Solar Empire\Sound\PlanetModule_PsiOrbitalFrigateFactory_OnSelection_0.ogg

you should now have 2 files:

PlanetModule_PsiOrbitalFrigateFactory_OnSelection_0.ogg

and

PlanetModule_PsiOrbitalFrigateFactory_OnSelection_0 - Copy.ogg

4) Rename  PlanetModule_PsiOrbitalFrigateFactory_OnSelection_0 - Copy.ogg to PlanetModule_TechOrbitalFrigateFactory_OnSelection_0.ogg

Now when you select the TEC Frigate Factory in the game, it doesn't have that straw sucking sound anymore.

I did the same thing for Frigate_TechLight_OnCreation.ogg using the UI_Common_Ping.ogg sound for a replacement.  It sounds great.  However, some sounds, like Quiet 1.ogg seem to break all the sounds if you use them as a replacement, so you might have to experiment.

I think this would make a KILLER MOD, because I agree - the sounds in this game are so bad that I stopped playing it!  The fastest way to do this is by writing a script for replacing the files in this directory.