If you haven't, run HotPocketRemix's Dark Souls unpacking tool. This will allow you to mod the game easily and doesn't require a bunch of extra work modding HEX 
or other stuff. 
Read about here:
https://www.reddit.com/r/darksouls/comments/60xu02/dark_souls_item_randomizer_v01_beta_testing/
DL Here:
https://github.com/HotPocketRemix/UnpackDarkSoulsForModding

After, you should have a sound folder in your Data folder.

BACKUP YOUR FILES! DO this before anything else. 

Then, Copy and paste all the files in the sound folder over the files in 
C:\Program Files (x86)\Steam\SteamApps\common\Dark Souls Prepare to Die Edition\DATA\sound


To change back, just copy and paste all the sound backups into the same folder.