There's a built in "override" folder for City of Heroes and as long as you know the name of the file to replace and the folder structure used in the backend system, you can place any sound you want in the "override" (called "data" in CoH) and the game will use YOUR version automatically!
I made a video showing the process, explaining how to find the sounds, how to extract the originals (for making louder and quieter), and how to replace them in-game. Ever wanted the "glowie" to scream at you like a weird goat? NOW YOU CAN!
