A lot of people probably know how to do this but when I wanted to do it I couldn't figure it out. Anyways, tools you need to do something like this are listed below.

Kotor Save Editor

Miles Sound Tools

Goldwave Digital Audio Editor

Now, if you've poked around the save editor before, you've probably noticed that there is an option to change soundsets, even on the notmally muted player character. If you want any of the normal soundsets listed there, you just click what you want, it's that easy. However, if you want to create a voice set for a character like Sion or Nihilus, you have to do a little more. The first thing you have to do is decide which NPC party soundset you want to overwrite. (I suggest party characters simply because they have options for opening chests, selecting them, etc.)

Overwriting sound files with a sound file is easy. Simply copy the file you want to use and rename it to the one you want to overwrite. Ex. Rename A_SITHASS_ATK to p_G0t0_Atk1.

If you want to overwrite a sound file with something from the StreamVoice folder, you have to decompress them with Miles Sound Tools first. Decompress them to a folder, and then rename and overwrite.

Then, simply go into the Save Editor and switch the soundsets. If you did it write, you should get an entirely new custom soundset.

PS- I put in goldwave in case you want to listen to the sound files before you overwrite them. I know that if you look around this is pretty easy to find, but I thought I might be able to put all this info in one place. Enjoy.

-Ledhead-

To create entirely new custom soundsets and distribute them as a mod, you don't have to overwrite any files.

The possibility to change the soundset with KSE was made more to allow the player to make quick changes when changing appearance, per example. Those changes a lost each time you load an earlier save or start a new game. For a more permanent solution, I suggest editing the .ssf file with Kotor tool.

Personally I try to avoid modifying original files inasmuch as possible so if people want to remove the mod, they can do it without having to reinstall the game or look for the files to rename during hours.

You can make new or edit existing soundset ( *.ssf) files with Kotor tool.

Start by adding your new sounds and name them whatever you want (no more than 16 characters), then, you add corresponding lines in the dialog.tlk file with a reference to your sound file in the SoundRef column. Save. Then launch Kotor tool's soundset editor, open the .sff file that corresponds to your npc and insert the reference to the new dialog.tlk file for each type of sound (attack, battlecry, etc.). (you can use stoffe's patcher to make your mod compatible with all others which is better than distributing a new dialog.tlk)

If you have a new npc, you can also create your custom .ssf file and add a line to soundsets.2da and then simply refer to that line in his .utc file.

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If you simply want to add existing sounds to into a .sff file such as adding some of Mandalore's sounds to complete Darth Sion's soundset file, then simply open Darth Sion's and Mandalore's .ssf files with Kotor tool and copy the additional contents from Mandalore's .ssf file into Darth Sion's. Drop the .ssf file into your override folder.